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An '''I/O port''' is usually used as a technical term for a specific address on the x86's IO bus. This bus provides communication with devices in a fixed order and size, and was used as an alternative to memory access. On many other architectures, there is no predefined bus for such communication and all communication with hardware is done via memory-mapped IO. This also increasingly happens on modern x86 hardware.
====I/O Ports====
Cleanup help requested!
<pre><nowiki>[This file was provided by Wim Osterholt (2:512/56 or wim@djo.wtm.tudelft.nl).]
Last Change: 11/6/94




== Looking for a list of ports ==
XT, AT and PS/2 I/O port addresses
As an operating system developer, '''you should not be looking for this'''. "Standardized" I/O ports are only used in some situations, such as hardware that was present on pre-PCI (AT and compatible, etc.) PC hardware. Examples of devices using "standardized" I/O ports are the [[Floppy Disk Controller|floppy drive]], [[Serial Ports|serial]] and [[Parallel port|parallel]] ports, However, most ports are claimed by plugin cards{{which}} you might not have and some{{which}} are even assigned via PNP which means that any port could be used for the device in question. If you want access to a device, you will need to look up the details for the device in question, and if some fixed port is involved, it will tell you. It is not technically feasible to have a complete mapping of ports to devices as you won't get access to it.


== Port abuse ==
Do NOT consider this information as complete and accurate.
A few devices{{which}} were made cheap and do not decode all address bits of the I/O port in question (only the bottom 12 or 14). That means that there are up to sixteen port addresses mapping to the same device.
If you want to do harware programming check ALWAYS the
Similarly, some devices have chosen to avoid conflict with such devices by using a sparse register file. The bottom bits would be defined as constant, and the ''top bits'' would instead be used for the index. You would get ports number <tt>0x82E8</tt>, <tt>0x84E8</tt>, <tt>0x86E8</tt> and so on. Such ISA devices are typically prone to interfering with [[PCI]] assigned IO addresses due to their spread.
appropriate data sheets. Be aware that erroneously programming
can put your hardware or your data at risk.


Modern implementations of old devices (typically IDE and VGA controllers) have an implementation that is mentioned to be plug-and-play with moving registers, but they are still able to listen to legacy ports and respond accordingly.
There is a memory mapped address in use for I/O functions of which I
think it should be mentioned here. See at the end of this list.


== The list ==
-------------------------------------------------------------------------------
If you have found a port number and you are still wondering what it's meant to do, here's a list of the most common ports:
0000-001F ---- DMA 1 (first Direct Memory Access controller 8237)
{| {{Wikitable}}
|-
!Port range
!Summary


|-
0000 r/w DMA channel 0 address byte 0, then byte 1.
|0x0000-0x001F
0001 r/w DMA channel 0 word count byte 0, then byte 1.
|The first legacy [[ISA DMA|DMA controller]], often used for transfers to floppies.
0002 r/w DMA channel 1 address byte 0, then byte 1.
0003 r/w DMA channel 1 word count byte 0, then byte 1.
0004 r/w DMA channel 2 address byte 0, then byte 1.
0005 r/w DMA channel 2 word count byte 0, then byte 1.
0006 r/w DMA channel 3 address byte 0, then byte 1.
0007 r/w DMA channel 3 word count byte 0, then byte 1.


|-
0008 r DMA channel 0-3 status register
|0x0020-0x0021
bit 7 = 1 channel 3 request
|The first [[PIC|Programmable Interrupt Controller]]
bit 6 = 1 channel 2 request
bit 5 = 1 channel 1 request
bit 4 = 1 channel 0 request
bit 3 = 1 channel terminal count on channel 3
bit 2 = 1 channel terminal count on channel 2
bit 1 = 1 channel terminal count on channel 1
bit 0 = 1 channel terminal count on channel 0


|-
0008 w DMA channel 0-3 command register
|0x0022-0x0023
bit 7 = 1 DACK sense active high
|Access to the Model-Specific Registers of Cyrix processors.
= 0 DACK sense active low
bit 6 = 1 DREQ sense active high
= 0 DREQ sense active low
bit 5 = 1 extended write selection
= 0 late write selection
bit 4 = 1 rotating priority
= 0 fixed priority
bit 3 = 1 compressed timing
= 0 normal timing
bit 2 = 1 enable controller
= 0 enable memory-to-memory


|-
0009 w DMA write request register
|0x0040-0x0047
|The [[PIT]] (Programmable Interval Timer)


|-
000A r/w DMA channel 0-3 mask register
|0x0060-0x0064
bit 7-3 = 0 reserved
|The [["8042" PS/2 Controller]] or its predecessors, dealing with keyboards and mice.
bit 2 = 0 clear mask bit
= 1 set mask bit
bit 1-0 = 00 channel 0 select
= 01 channel 1 select
= 10 channel 2 select
= 11 channel 3 select


|-
000B w DMA channel 0-3 mode register
|0x0070-0x0071
bit 7-6 = 00 demand mode
|The [[CMOS]] and [[RTC]] registers
= 01 single mode
= 10 block mode
= 11 cascade mode
bit 5 = 0 address increment select
= 1 address decrement select
bit 3-2 = 00 verify operation
= 01 write to memory
= 10 read from memory
= 11 reserved
bit 1-0 = 00 channel 0 select
= 01 channel 1 select
= 10 channel 2 select
= 11 channel 3 select


|-
000C w DMA clear byte pointer flip-flop
|0x0080-0x008F
000D r DMA read temporary register
|The [[DMA]] (Page registers)
000D w DMA master clear
000E w DMA clear mask register
000F w DMA write mask register


|-
-------------------------------------------------------------------------------
|0x0092
0010-001F ---- DMA controller (8237) on PS/2 model 60 & 80
|The location of the fast [[A20]] gate register


|-
-------------------------------------------------------------------------------
|0x00A0-0x00A1
0018 w PS/2 extended function register
|The second [[PIC]]


|-
-------------------------------------------------------------------------------
|0x00C0-0x00DF
001A PS/2 extended function execute
|The second [[DMA]] controller, often used for soundblasters


|-
-------------------------------------------------------------------------------
|0x00E9
0020-003F ---- PIC 1 (Programmable Interrupt Controller 8259)
|Home of the [[Bochs|Port E9 Hack]]. Used on some emulators to directly send text to the hosts' console.


|-
0020 w PIC initialization command word ICW1
|0x0170-0x0177
bit 7-5 = 0 only used in 80/85 mode
|The secondary [[ATA]] harddisk controller.
bit 4 = 1 ICW1 is being issued
bit 3 = 0 edge triggered mode
= 1 level triggered mode
bit 2 = 0 successive interrupt vectors use 8 bytes
= 1 successive interrupt vectors use 4 bytes
bit 1 = 0 cascade mode
= 1 single mode, no ICW3 needed
bit 0 = 0 no ICW4 needed
= 1 ICW4 needed


|-
0021 w PIC ICW2,ICW3,ICW4 after ICW1 to 0020
|0x01F0-0x01F7
ICW2:
|The primary [[ATA]] harddisk controller.
bit 7-3 = address lines A0-A3 of base vector address for PIC
bit 2-0 = reserved
ICW3:
bit 7-0 = 0 slave controller not attached to corresponding
interrupt pin
= 1 slave controller attached to corresponding
interrupt pin
ICW4:
bit 7-5 = 0 reserved
bit 4 = 0 no special fully-nested mode
= 1 special fully-nested mode
bit 3-2 = 0x nonbuffered mode
= 10 buffered mode/slave
= 11 buffered mode/master
bit 1 = 0 normal EOI
= 1 Auto EOI
bit 0 = 0 8085 mode
= 1 8086/8088 mode


|-
0021 r/w PIC master interrupt mask register
|0x0278-0x027A
OCW1:
|Parallel port
bit 7 = 0 enable parallel printer interrupt
bit 6 = 0 enable diskette interrupt
bit 5 = 0 enable fixed disk interrupt
bit 4 = 0 enable serial port 1 interrupt
bit 3 = 0 enable serial port 2 interrupt
bit 2 = 0 enable video interrupt
bit 1 = 0 enable keyboard, mouse, RTC interrupt
bit 0 = 0 enable timer interrupt


|-
0020 r PIC interrupt request/in-service registers by OCW3
|0x02F8-0x02FF
request register:
|Second [[Serial Ports|serial port]]
bit 7-0 = 0 no active request for the corresponding int. line
= 1 active request for corresponding interrupt line
in-service register:
bit 7-0 = 0 corresponding line not currently being serviced
= 1 corresponding int. line currently being serviced


|-
0020 w OCW2:
|0x03B0-0x03DF
bit 7-5 = 000 rotate in auto EOI mode (clear)
|The range used for the [[VGA Hardware|IBM VGA]], its direct predecessors, as well as any modern video card in legacy mode.
= 001 nonspecific EOI
= 010 no operation
= 011 specific EOI
= 100 rotate in auto EOI mode (set)
= 101 rotate on nonspecific EOI command
= 110 set priority command
= 111 rotate on specific EOI command
bit 4 = 0 reserved
bit 3 = 0 reserved
bit 2-0 interrupt request to which the command applies


|-
0020 w PIC OCW3
|0x03F0-0x03F7
bit 7 = 0 reserved
|[[FDC|Floppy disk controller]]
bit 6-5 = 0x no operation
= 10 reset special mask
= 11 set special mask
bit 4 = 0 reserved
bit 3 = 1 reserved
bit 2 = 0 no poll command
= 1 poll command
bit 1-0 = 0x no operation
= 10 read int.request register on next read at 0020
= 11 read int.in-service register on next read 0020


|-
-------------------------------------------------------------------------------
|0x03F8-0x03FF
0022-002B ---- Intel 82355, part of chipset for 386sx
|First [[Serial Ports|serial port]]
initialisation in POST will disable these addresses,
only a hard reset will enable them again.


|}
0022 r/w 82335 MCR memory configuration register
0024 82335 RC1 roll compare register
0026 82335 RC2 roll compare register
0028 82335 CC0 compare register
002A 82335 CC1 compare register


== See Also ==
values for CC0 and CC1:
00F9,0000 enable range compare CC0 0-512K CC1 disable
00F1,0000 enable range compare CC0 0-1024K CC1 disable
00F1,10F9 enable range compare CC0 0-1M CC1 1M-1M5
00E1,0000 enable range compare CC0 0-2M CC1 disable
00E1,0000 enable range compare CC0 0-2M CC1 disable
00C1,0000 enable range compare CC0 0-4M CC1 disable
00C1,40E1 enable range compare CC0 0-4M CC1 4M-6M
0081,0000 enable range compare CC0 0-8M CC1 disable


=== External Links ===
-------------------------------------------------------------------------------
* [http://bochs.sourceforge.net/techspec/PORTS.LST Bochs' map of I/O ports to functions]
0022-0023 ---- Chip Set Data


[[Category:X86]]
0022 w index for accesses to data port
0023 r/w chip set data

-------------------------------------------------------------------------------
0022-0023 ---- Cyrix Cx486SLC/DLC processor Cache Configuration Registers

0022 w index for accesses to next port
C0h CR0
C1h CR1
C4h non-cacheable region 1, start address bits 31-24
C5h non-cacheable region 1, start address bits 23-16
C6h non-cacheable region 1, start addr 15-12, size (low nibble)
C7h non-cacheable region 2, start address bits 31-24
C8h non-cacheable region 2, start address bits 23-16
C9h non-cacheable region 2, start addr 15-12, size (low nibble)
CAh non-cacheable region 3, start address bits 31-24
CBh non-cacheable region 3, start address bits 23-16
CCh non-cacheable region 3, start addr 15-12, size (low nibble)
CDh non-cacheable region 4, start address bits 31-24
CEh non-cacheable region 4, start address bits 23-16
CFh non-cacheable region 4, start addr 15-12, size (low nibble)
0023 r/w cache configuration register array (indexed by port 0022h)

non-cacheable region sizes:
00h disabled
01h 4K
02h 8K
03h 16K
04h 32K
05h 64K
06h 128K
07h 256K
08h 512K
09h 1M
0Ah 2M
0Bh 4M
0Ch 8M
0Dh 16M
0Eh 32M
0Fh 4G

Configuration Register 0 format:
bit 0 "NC0" first 64K of each 1M noncacheable in real/V86
bit 1 "NC1" 640K-1M noncacheable
bit 2 "A20M" enables A20M# input pin
bit 3 "KEN" enables KEN# input pin
bit 4 "FLUSH" enables KEN# input pin
bit 5 "BARB" enables internal cache flushing on bus holds
bit 6 "C0" cache direct-mapped instead of 2-way associative
bit 7 "SUSPEND" enables SUSP# input and SUSPA# output pins

Configuration Register 1 format;
bit 0 "RPL" enables output pins RPLSET and RPLVAL#

-------------------------------------------------------------------------------
0026-0027 ---- Power Management

0026 w index for data port
0027 r/w power management data

-------------------------------------------------------------------------------
0038-003F ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
0040-005F ---- PIT (Programmable Interrupt Timer 8253, 8254)
XT & AT uses 40-43 PS/2 uses 40, 42,43,44, 47

0040 r/w PIT counter 0, counter divisor (XT, AT, PS/2)
0041 r/w PIT counter 1, RAM refresh counter (XT, AT)
0042 r/w PIT counter 2, cassette & speaker (XT, AT, PS/2)

0043 r/w PIT mode port, control word register for counters 0-2
bit 7-6 = 00 counter 0 select
= 01 counter 1 select (not PS/2)
= 10 counter 2 select
bit 5-4 = 00 counter latch command
= 01 read/write counter bits 0-7 only
= 10 read/write counter bits 8-15 only
= 11 read/write counter bits 0-7 first, then 8-15
bit 3-1 = 000 mode 0 select
= 001 mode 1 select - programmable one shot
= x10 mode 2 select - rate generator
= x11 mode 3 select - square wave generator
= 100 mode 4 select - software triggered strobe
= 101 mode 5 select - hardware triggered strobe
bit 0 = 0 binary counter 16 bits
= 1 BCD counter

0044 r/w PIT counter 3 (PS/2, EISA)
used as fail-safe timer. generates an NMI on time out.
for user generated NMI see at 0462.

0047 w PIT control word register counter 3 (PS/2, EISA)
bit 7-6 = 00 counter 3 select
= 01 reserved
= 10 reserved
= 11 reserved
bit 5-4 = 00 counter latch command counter 3
= 01 read/write counter bits 0-7 only
= 1x reserved
bit 3-0 = 00

0048 EISA
0049 8254 timer 2, not used (counter 1)
004A EISA programmable interval timer 2
004B EISA programmable interval timer 2

-------------------------------------------------------------------------------
0060-006F ---- Keyboard controller 804x (8041, 8042) (or PPI (8255) on PC,XT)
XT uses 60-63, AT uses 60-64

AT keyboard controller input port bit definitions
bit 7 = 0 keyboard inhibited
bit 6 = 0 CGA, else MDA
bit 5 = 0 manufacturing jumper installed
bit 4 = 0 system RAM 512K, else 640K
bit 3-0 reserved

AT keyboard controller input port bit definitions by Compaq
bit 7 = 0 security lock is locked
bit 6 = 0 Compaq dual-scan display, 1=non-Compaq display
bit 5 = 0 system board dip switch 5 is ON
bit 4 = 0 auto speed selected, 1=high speed selected
bit 3 = 0 slow (4MHz), 1 = fast (8MHz)
bit 2 = 0 80287 installed, 1= no NDP installed
bit 1-0 reserved

AT keyboard controller output port bit definitions
bit 7 = keyboard data output
bit 6 = keyboard clock output
bit 5 = 0 input buffer full
bit 4 = 0 output buffer empty
bit 3 = reserved (see note)
bit 2 = reserved (see note)
bit 1 = gate A20
bit 0 = system reset
Note: bits 2 and 3 are the turbo speed switch or password
lock on Award/AMI/Phoenix BIOSes. These bits make
use of nonstandard keyboard controller BIOS
functionality to manipulate
pin 23 (8041 port 22) as turbo switch for AWARD
pin 35 (8041 port 15) as turbo switch/pw lock for
Phoenix

0060 r/w KB controller data port or keyboard input buffer (ISA, EISA)
should only be read from after status port bit0 = 1
should only be written to if status port bit1 = 0
keyboard commands (data also goes to port 0060):
E6 sngl set mouse scaling to 1:1
E7 sngl set mouse scaling to 2:1
E8 dbl set mouse resolution
(00h = 1/mm,01h = 2/mm,02h = 4/mm,03h = 8/mm)
E9 sngl get mouse information
read two status bytes:
byte 0
bit 7 unused
bit 6 remote rather than stream mode
bit 5 mouse enabled
bit 4 scaling set to 2:1
bit 3 unused
bit 2 left button pressed
bit 1 unused
bit 0 right button pressed
byte 1: resolution
ED dbl set/reset mode indicators Caps Num Scrl
bit 2 = CapsLk, bit 1 = NumLk, bit 0 = ScrlLk
EE sngl diagnostic echo. returns EE.
EF sngl NOP (No OPeration). reserved for future use
F0 dbl get/set scan code set
00h get current set
01h scancode set 1 (except Type 2 ctrlr)
02h scancode set 2 (default)
03h scancode set 3
F2 sngl read keyboard ID (read two ID bytes)
F2 sngl read mouse ID (read two ID bytes)
F3 dbl set typematic rate/delay
F3 dbl set mouse sample rate in reports per second
F4 sngl enable keyboard
F4 sngl enable mouse
F5 sngl disable keyboard. set default parameters
F5 sngl disable mouse, set default parameters
F6 sngl set default parameters
F7 sngl [MCA] set all keys to typematic (scancode set 3)
F8 sngl [MCA] set all keys to make/release
F9 sngl [MCA] set all keys to make only
FA sngl [MCA] set all keys to typematic/make/release
FB sngl [MCA] set al keys to typematic
FC dbl [MCA] set specific key to make/release
FD dbl [MCA] set specific key to make only
FE sngl resend last scancode
FF sngl perform internal power-on reset function
FF sngl reset mouse
Note: must issue command D4h to port 64h first to access
mouse functions


0060 r KeyBoard or KB controller data output buffer (via PPI on XT)

0061 w KB controller port B (ISA, EISA) (PS/2 port A is at 0092)
system control port for compatibility with 8255
bit 7 (1= IRQ 0 reset )
bit 6-4 reserved
bit 3 = 1 channel check enable
bit 2 = 1 parity check enable
bit 1 = 1 speaker data enable
bit 0 = 1 timer 2 gate to speaker enable

0061 r KB controller port B control register (ISA, EISA)
system control port for compatibility with 8255
bit 7 parity check occurred
bit 6 channel check occurred
bit 5 mirrors timer 2 output condition
bit 4 toggles with each refresh request
bit 3 channel check status
bit 2 parity check status
bit 1 speaker data status
bit 0 timer 2 gate to speaker status

0061 w PPI Programmable Peripheral Interface 8255 (XT only)
system control port
bit 7 = 1 clear keyboard
bit 6 = 0 hold keyboard clock low
bit 5 = 0 I/O check enable
bit 4 = 0 RAM parity check enable
bit 3 = 0 read low switches
bit 2 reserved, often used as turbo switch
bit 1 = 1 speaker data enable
bit 0 = 1 timer 2 gate to speaker enable

0062 r/w PPI (XT only)
bit 7 = 1 RAM parity check
bit 6 = 1 I/O channel check
bit 5 = 1 timer 2 channel out
bit 4 reserved
bit 3 = 1 system board RAM size type 1
bit 2 = 1 system board RAM size type 2
bit 1 = 1 coprocessor installed
bit 0 = 1 loop in POST

0063 r/w PPI (XT only) command mode register (read dipswitches)
bit 7-6 = 00 1 diskette drive
= 01 2 diskette drives
= 10 3 diskette drives
= 11 4 diskette drives
bit 5-4 = 00 reserved
= 01 40*25 color (mono mode)
= 10 80*25 color (mono mode)
= 11 MDA 80*25
bit 3-2 = 00 256K (using 256K chips)
= 01 512K (using 256K chips)
= 10 576K (using 256K chips)
= 11 640K (using 256K chips)
bit 3-2 = 00 64K (using 64K chips)
= 01 128K (using 64K chips)
= 10 192K (using 64K chips)
= 11 256K (using 64K chips)
bit 1-0 reserved

0064 r KB controller read status (ISA, EISA)
bit 7 = 1 parity error on transmission from keyboard
bit 6 = 1 receive timeout
bit 5 = 1 transmit timeout
bit 4 = 0 keyboard inhibit
bit 3 = 1 data in input register is command
0 data in input register is data
bit 2 system flag status: 0=power up or reset 1=selftest OK
bit 1 = 1 input buffer full (input 60/64 has data for 8042)
bit 0 = 1 output buffer full (output 60 has data for system)

0064 r KB controller read status (MCA)
bit 7 = 1 parity error on transmission from keyboard
bit 6 = 1 general timeout
bit 5 = 1 mouse output buffer full
bit 4 = 0 keyboard inhibit
bit 3 = 1 data in input register is command
0 data in input register is data
bit 2 system flag status: 0=power up or reset 1=selftest OK
bit 1 = 1 input buffer full (input 60/64 has data for 804x)
bit 0 = 1 output buffer full (output 60 has data for system)

0064 r KB controller read status by Compaq
bit 7 = 1 parity error detected (11-bit format only). If an
error is detected, a Resend command is sent to the
keyboard once only, as an attempt to recover.
bit 6 = 1 receive timeout. transmission didn't finish in 2mS.
bit 5 = 1 transmission timeout error
bit 5,6,7 cause
1 0 0 No clock
1 1 0 Clock OK, no response
1 0 1 Clock OK, parity error
bit 4 = 0 security lock engaged
bit 3 = 1 data in OUTPUT register is command
0 data in OUTPUT register is data
bit 2 system flag status: 0=power up or reset 1=soft reset
bit 1 = 1 input buffer full (output 60/64 has data)
bit 0 = 0 no new data in buffer (input 60 has data)

0064 w KB controller input buffer (ISA, EISA)
KB controller commands (data goes to port 0060):
20 read read byte zero of internal RAM, this is the
last KB command send to 804x
Compaq Put current command byte on port 0060
command structure:
bit 7 reserved
bit 6 = 1 convert KB codes to 8086 scan codes
bit 5 = 0 use 11-bit codes, 1=use 8086 codes
bit 4 = 0 enable keyboard, 1=disable keyboard
bit 3 = 1 ignore security lock state
bit 2 this bit goes into bit2 status reg.
bit 1 = 0 reserved
bit 0 = 1 generate int. when output buffer full
21-3F read reads the byte specified in the lower 5 bits of
the command in the 804x's internal RAM
60-7F dbl writes the data byte to the address specified in
the 5 lower bits of the command.

Alternate description KB IO command 60 summary:
bit7 = 0 reserved
bit6 = IBM PC compatibility mode
bit5 = IBM PC mode
bit4 = disable kb
bit3 = inhibit override
bit2 = system flag
bit1 = 0 reserved
bit0 = enableoutput buffer full interrupt

60 Compaq Load new command (60 to [64], command to [60])
A1 Compaq unknown speedfunction ??
A2 Compaq unknown speedfunction ??
A3 Compaq Enable system speed control
A4 MCA check if password installed
A4 Compaq Toggle speed
A5 MCA load password
A5 Compaq Special reed. the 8042 places the real values
of port 2 except for bits 4 and 5 wich are given
a new definition in the output buffer. No output
buffer full is generated.
if bit 5 = 0, a 9-bit keyboard is in use
if bit 5 = 1, an 11-bit keyboard is in use
if bit 4 = 0, outp-buff-full interrupt disabled
if bit 4 = 1, output-buffer-full int. enabled
A6 MCA check password
A6 Compaq unknown speedfunction ??
A7 MCA disable mouse port
A8 MCA enable mouse port
A9 MCA test mouse port
AA sngl initiate self-test. will return 55 to data port
Compaq Initializes ports 1 and 2, disables the keyboard
and clears the buffer pointers. It then places
55 in the output buffer.
AB sngl initiate interface test. result values:
0 = no error
1 = keyboard clock line stuck low
2 = keyboard clock line stuck high
3 = keyboard data line is stuck low
4 = keyboard data line stuck high
Compaq 5 = Compaq diagnostic feature
AC read diagnostic dump. the contents of the 804x RAM,
output port, input port, status word are send.
AD sngl disable keyboard (sets bit 4 of commmand byte)
AE sngl enable keyboard (resets bit 4 of commmand byte)
AF AWARD Enhanced Command: read keyboard version
C0 read read input port
Compaq Places status of input port in output buffer. use
this command only when the output buffer is empty
C1 MCA Enhanced Command: poll input port Low nibble
C2 MCA Enhanced Command: poll input port High nibble
D0 read read output port
Compaq Places byte in output port in output buffer. use
this command only when the output buffer is empty
D1 dbl write output port. next byte written to 0060
will be written to the 804x output port; the
original IBM AT and many compatibles use bit 1 of
the output port to control the A20 gate.
Compaq The system speed bits are not set by this command
use commands A1-A6 (!) for speed functions.
D2 MCA Enhanced Command: write keyboard output buffer
D3 MCA Enhanced Command: write pointing device out.buf.
D4 MCA write to mouse
D4 AWARD Enhanced Command: write to auxiliary device
DD sngl disable address line A20 (HP Vectra only???)
default in Real Mode
DF sngl enable address line A20 (HP Vectra only???)
E0 read read test inputs.
bit0 = kbd clock, bit1 = kbd data
Exxx AWARD Enhanced Command: active output port
ED Compaq This is a two part command to control the state
of the NumLock CpasLock and ScrollLock LEDs
The second byte contains the state to set LEDs.
bit 7-3 reserved. should be set to 0.
bit 2 = 0 Caps Lock LED off
bit 1 = 0 Num Lock LED off
bit 0 = 0 Scroll Lock LED off
F0-FF sngl pulse output port low for 6 microseconds.
bits 0-3 contain the mask for the bits to be
pulsed. a bit is pulsed if its mask bit is zero.
bit0=system reset. Don't set to zero. Pulse only!

general note: Keyboard controllers are widely different from each other.
You cannot generally exchange them between different machines.
note on Award: Derived from Award's Enhanced KB controller advertising sheet.
note on Compaq: Derived from the Compaq Deskpro 386 Tech. Ref. Guide.

0065 r communications port (Olivetti M24)

0068 w HP-Vectra control buffer (HP commands)
0069 r HP-Vectra SVC (keyboard request SerViCe port)
006A w HP-Vectra clear processing, done

006C-006F HP-HIL (Human Interface Link = async. serial inputs 0-7)

-------------------------------------------------------------------------------
0065 ---- AT&T 6300+ high/low chip select

-------------------------------------------------------------------------------
0065 ---- ???

0065 r/w ???
bit 2: A20 gate control (set = A20 enabled, clear = disabled)

-------------------------------------------------------------------------------
0066-0067 ---- AT&T 6300+ system configuration switches

-------------------------------------------------------------------------------
0068 ---- C&T chipsets, turbo mode control

-------------------------------------------------------------------------------
006B-006F ---- SSGA control registers

006B ? RAM enable/remap
006C-006F undocumented

-------------------------------------------------------------------------------
0070-007F ---- CMOS RAM/RTC (Real Time Clock MC146818)

0070 w CMOS RAM index register port (ISA, EISA)
bit 7 = 1 NMI disabled
= 0 NMI enabled
bit 6-0 CMOS RAM index (64 bytes, sometimes 128 bytes)

any write to 0070 should be followed by an action to 0071
or the RTC wil be left in an unknown state.

0071 r/w CMOS RAM data port (ISA, EISA)
RTC registers:
00 current second in BCD
01 alarm second in BCD
02 current minute in BCD
03 alarm minute in BCD
04 current hour in BCD
05 alarm hour in BCD
06 day of week in BCD
07 day of month in BCD
08 month in BCD
09 year in BCD (00-99)
0A status register A
bit 7 = 1 update in progress
bit 6-4 divider that identifies the time-based
frequency
bit 3-0 rate selection output frequency and int. rate
0B status register B
bit 7 = 0 run
= 1 halt
bit 6 = 1 enable periodic interrupt
bit 5 = 1 enable alarm interrupt
bit 4 = 1 enable update-ended interrupt
bit 3 = 1 enable square wave interrupt
bit 2 = 1 calendar is in binary format
= 0 calendar is in BCD format
bit 1 = 1 24-hour mode
= 0 12-hour mode
bit 0 = 1 enable daylight savings time. only in USA.
useless in Europe. Some DOS versions clear
this bit when you use the DAT/TIME command.
0C status register C
bit 7 = interrupt request flag
bit 6 = peridoc interrupt flag
bit 5 = alarm interrupt flag
bit 4 = update interrupt flag
bit 3-0 reserved
0D status register D
bit 7 = 1 Real-Time Clock has power
bit 6-0 reserved
0E diagnostics status byte
bit 7 = 0 RTC lost power
bit 6 = 1 CMOS RAM checksum bad
bit 5 = 1 invalid configuration information at POST
bit 4 = 1 memory size error at POST
bit 3 = 1 fixed disk/adapter failed initialization
bit 2 = 1 CMOS RAM time found invalid
bit 1 = 1 adapters do not match configuration (EISA)
bit 0 = 1 time out reading an adapter ID (EISA)
0F shutdown status byte
00 = normal execution of POST
01 = chip set initialization for real mode reentry
04 = jump to bootstrap code
05 = issue an EOI an JMP to Dword ptr at 40:67
06 = JMP to Dword ptrv at 40:67 without EOI
07 = return to INT15/87 (block move)
08 = return to POST memory test
09 = return to INT15/87 (block move)
0A = JMP to Dword ptr at 40:67 without EOI
0B = return IRETS through 40:67
10 diskette drive type for A: and B:
bit 7-4 drive type of drive 0
bit 3-0 drive type of drive 1
= 0000 no drive
= 0001 360K
= 0010 1M2
= 0011 720K
= 0100 1M44
= 0101-1111 reserved
11 reserved / AMI Extended CMOS setup (AMI Hi-Flex BIOS)
bit 7 = 1 Typematic Rate Programming
bit 6-5 = 00 Typematic Rate Delay 250 mSec
bit 4-0 = 00011 Typematic Rate 21.8 Chars/Sec
12 fixed disk drive type for drive 0 and drive 1
bit 7-4 drive type of drive 0
bit 3-0 drive type of drive 1
if either of the nibbles equals 0F, then bytes
19 an 1A are valid
13 reserved / AMI Extended CMOS setup (AMI Hi-Flex BIOS)
bit 7 = 1 Mouse Support Option
bit 6 = 1 Above 1 MB Memory Test disable
bit 5 = 1 Memory Test Tick Sound disable
bit 4 = 1 Memory Parity Error Check enable
bit 3 = 1 Hit <ESC> Message Display disabled
bit 2 = 1 Hard Disk Type 47 Data Area at address 0:300
bit 1 = 1 Wait For <F1> If Any Error enabled
bit 0 = 1 System Boot Up Num Lock is On
14 equipment byte
bit 7-6 diskette drives installed
= 00 1 drive installed
= 01 2 drives installed
= 10 reserved
= 11 reserved
bit 5-4 primary display
= 00 adapter card with option ROM
= 01 40*25 color
= 10 80*25 color
= 11 monochrome
bit 3-2 reserved
bit 1 = 1 coprocessor installed (non-Weitek)
bit 0 diskette drive avaliable for boot
15 LSB of systemn base memory in Kb
16 MSB of systemn base memory in Kb
17 LSB of total extended memory in Kb
18 MSB of total extended memory in Kb
19 drive C extension byte
1A drive D extension byte
1B-27 reserved
1B/1C word to 82335 RC1 roll compare register at [24]
(Phoenix)
1D/1E word to 82335 RC2 roll compare register at [26]
(Phoenix)
28 HP-Vectra checksum over 29-2D
29-2D reserved
29/2A word to Intel 82335 CC0 compare register at
[28](Phoenix)
2B/2C word send to 82335 CC1 compare register at [2A]
(Phoenix)
2D AMI Extended CMOS setup (AMI Hi-Flex BIOS)
(Phoenix BIOS checks for the values AA or CC)
bit 7 = 1 Weitek Processor Absent
bit 6 = 1 Floppy Drive Seek At Boot disabled
bit 5 = 1 System Boot Up Sequence C:, A:
bit 4 = 1 System Boot Up Speed is high
bit 3 = 1 Cache Memory enabled
bit 2 = 1 Internal Cache Memory <1>
bit 1-0 reserved
2E CMOS MSB checksum over 10-2D
2F CMOS LSB checksum over 10-2D
30 LSB of extended memory found above 1Mb at POST
31 MSB of extended memory found above 1Mb at POST
32 date century in BCD
33 information flags
bit4 = bit4 from CPU register CR0 (Phoenix)
this bit is only known as INTEL RESERVED
34-3F reserved
34 bit4 bit5 (Phoenix BIOS)
3D/3E word to 82335 MCR memory config register at
[22](Phoenix)
3D bit3 base memsize 512/640 (Phoenix)
3E bit7 = 1 relocate enable (Phoenix)
bit1 = 1 shadow video enable (Phoenix)
bit0 = 1 shadow BIOS enable (Phoenix)


User Definable Drive Parameters are also stored in CMOS RAM:

AMI (386sx BIOS 1989) first user definable drive (type 47)
1B L cylinders
1C H cylinders
1D heads
1E L Write Precompensation Cylinder
1F H Write Precompensation Cylinder
20 ??
21 L cylinders parking zone
22 H cylinders parking zone
23 sectors

AMI (386sx BIOS 1989) second user definable drive (type 48)
24 L cylinders
25 H cylinders
26 heads
27 L Write Precompensation Cylinder
28 H Write Precompensation Cylinder
29 ??
2A L cylinders parking zone
2B H cylinders parking zone
2C sectors

Phoenix (386BIOS v1.10.03 1988) 1st user definable drv (type48)
20 L cylinders
21 H cylinders
22 heads
23 L Write Precompensation Cylinder
24 H Write Precompensation Cylinder
25 L cylinders parking zone
26 H cylinders parking zone
27 sectors

Phoenix (386BIOS v1.10.03 1988) 2nd user definable drv (type49)
(when PS/2-style password option is not used)
35 L cylinders
36 H cylinders
37 heads
38 L Write Precompensation Cylinder
39 H Write Precompensation Cylinder
3A L cylinders parking zone
3B H cylinders parking zone
3C sectors

- - - - - - - - ---------------------------------------------------------------
0073 ---- Intel Pentium motherboard ("Neptune" chipset)

0073 r/w bit 7: ???

- - - - - - - - ---------------------------------------------------------------
0074-0076 secondary CMOS (Compaq)

0074 w secondary CMOS RAM index (Compaq)

0076 r/w secondary CMOS RAM (Compaq)

- - - - - - - - ---------------------------------------------------------------
0078 HP-Vectra Hard Reset: NMI enable/disable
bit 7 = 0 disable & clear hard reset from HP-HIL controller
= 1 enable hard reset from HP-HIL controller chip
bit 6-0 reserved

-------------------------------------------------------------------------------
0078-007F ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
007C-007D ---- HP-Vectra PIC 3 (Programmable Interrupt Controller 8259)
cascaded to first controller.
used for keyboard and input device interface.
007C r/w HP-Vectra PIC 3 see at 0020 PIC 1
007D r/w HP-Vectra PIC 3 see at 0021 PIC 1

-------------------------------------------------------------------------------
0080 w Manufacturing Diagnostics port

-------------------------------------------------------------------------------
0080-008F ---- DMA page registers (74612)

0080 r/w extra page register (temporary storage)
0081 r/w DMA channel 2 address byte 2
0082 r/w DMA channel 3 address byte 2
0083 r/w DMA channel 1 address byte 2
0084 r/w extra page register
0085 r/w extra page register
0086 r/w extra page register
0087 r/w DMA channel 0 address byte 2
0088 r/w extra page register
0089 r/w DMA channel 6 address byte 2
0089 r/w DMA channel 7 address byte 2
0089 r/w DMA channel 5 address byte 2
008C r/w extra page register
008D r/w extra page register
008E r/w extra page register
008F r/w DMA refresh page register

-------------------------------------------------------------------------------
0084 ---- Compaq POST Diagnostic

-------------------------------------------------------------------------------
0084 ---- EISA Synchronize Bus Cycle

-------------------------------------------------------------------------------
0090-009F ---- PS/2 POS (Programmable Option Select)

0090 Central arbitration control port
0091 r Card selection feedback

0092 r/w PS/2 system control port A (port B is at 0061)
bit 7-6 any bit set to 1 turns activity light on
bit 5 reserved
bit 4 = 1 watchdog timout occurred
bit 3 = 0 RTC/CMOS security lock (on password area) unlocked
= 1 CMOS locked (done by POST)
bit 2 reserved
bit 1 = 1 indicates A20 active
bit 0 = 0 system reset or write
1 pulse alternate reset pin (alternate CPU reset)

0094 w system board enable/setup register
bit 7 = 1 enable functions
= 0 setup functions
bit 5 = 1 enables VGA
= 0 setup VGA

0095 reserved

0096 w adapter enable /setup register
bit 3 = 1 setup adapters
= 0 enable registers

0097 reserved

-------------------------------------------------------------------------------
00A0-00AF ---- PIC 2 (Programmable Interrupt Controller 8259)

00A0 r/w NMI mask register (XT)

00A0 r/w PIC 2 same as 0020 for PIC 1
00A1 r/w PIC 2 same as 0021 for PIC 1 except for OCW1:
bit 7 = 0 reserved
bit 6 = 0 enable fixed disk interrupt
bit 5 = 0 enable coprocessor exception interrupt
bit 4 = 0 enable mouse interrupt
bit 3 = 0 reserved
bit 2 = 0 reserved
bit 1 = 0 enable redirect cascade
bit 0 = 0 enable real-time clock interrupt

-------------------------------------------------------------------------------
00B0-00BF ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
00C0 ---- TI SN746496 programmable tone/noise generator PCjr

-------------------------------------------------------------------------------
00C0-00DF ---- DMA 2 (second Direct Memory Access controller 8237)

00C0 r/w DMA channel 4 memory address bytes 1 and 0 (low) (ISA, EISA)
00C2 r/w DMA channel 4 transfer count bytes 1 and 0 (low) (ISA, EISA)
00C4 r/w DMA channel 5 memory address bytes 1 and 0 (low) (ISA, EISA)
00C6 r/w DMA channel 5 transfer count bytes 1 and 0 (low) (ISA, EISA)
00C8 r/w DMA channel 6 memory address bytes 1 and 0 (low) (ISA, EISA)
00CA r/w DMA channel 6 transfer count bytes 1 and 0 (low) (ISA, EISA)
00CC r/w DMA channel 7 memory address byte 0 (low), then 1 (ISA, EISA)
00CE r/w DMA channel 7 transfer count byte 0 (low), then 1 (ISA, EISA)

00D0 r DMA channel 4-7 status register (ISA, EISA)
bit 7 = 1 channel 7 request
bit 6 = 1 channel 6 request
bit 5 = 1 channel 5 request
bit 4 = 1 channel 4 request
bit 3 = 1 terminal count on channel 7
bit 2 = 1 terminal count on channel 6
bit 1 = 1 terminal count on channel 5
bit 0 = 1 terminal count on channel 4

00D0 w DMA channel 4-7 command register (ISA, EISA)
bit 7 = 1 DACK sense active high
= 0 DACK sense active low
bit 6 = 1 DREQ sense active high
= 0 DREQ sense active low
bit 5 = 1 extended write selection
= 0 late write selection
bit 4 = 1 rotating priority
= 0 fixed priority
bit 3 = 1 compressed timing
= 0 normal timing
bit 2 = 0 enable controller
bit 1 = 1 enable memory-to-memory transfer
bit 0 .....

00D2 w DMA channel 4-7 write request register (ISA, EISA)

00D4 w DMA channel 4-7 write single mask register (ISA, EISA)
bit 7-3 reserved
bit 2 = 0 clear mask bit
= 1 set mask bit
bit 1-0 = 00 channel 4 select
= 01 channel 5 select
= 10 channel 6 select
= 11 channel 7 select

00D6 w DMA channel 4-7 mode register (ISA, EISA)
bit 7-6 = 00 demand mode
= 01 single mode
= 10 block mode
= 11 cascade mode
bit 5 = 0 address increment select
= 1 address decrement select
bit 4 = 0 autoinitialisation disable
= 1 autoinitialisation enable
bit 3-2 = 00 verify operation
= 01 write to memory
= 10 read from memory
= 11 reserved
bit 1-0 = 00 channel 4 select
= 01 channel 5 select
= 10 channel 6 select
= 11 channel 7 select

00D8 w DMA channel 4-7 clear byte pointer flip-flop (ISA, EISA)
00DA r DMA channel 4-7 read temporary register (ISA, EISA)
00DA w DMA channel 4-7 master clear (ISA, EISA)
00DC w DMA channel 4-7 clear mask register (ISA, EISA)
00DE w DMA channel 4-7 write mask register (ISA, EISA)

-------------------------------------------------------------------------------
00E0-00E7 ---- Microchannel

00E0 r/w split address register, memory encoding registers PS/2m80 only
00E1 r/w memory register
00E3 r/w error trace
00E4 r/w error trace
00E5 r/w error trace
00E7 r/w error trace

-------------------------------------------------------------------------------
00F0-00F5 ---- PCjr Disk Controller

00F0 disk controller
00F2 disk controller control port
00F4 disk controller status register
00F5 disk controller data port

-------------------------------------------------------------------------------
00F0-00FF ---- coprocessor (8087..80387)

00F0 w math coprocessor clear busy latch
00F1 w math coprocessor reset
00F8 r/w opcode transfer
00FA r/w opcode transfer
00FC r/w opcode transfer

-------------------------------------------------------------------------------
00F9-00FF ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
0100-010F ---- CompaQ Tape drive adapter. alternate address at 0300

-------------------------------------------------------------------------------
0100-0107 ---- PS/2 POS (Programmable Option Select)

0100 r POS register 0 Low adapter ID byte
0101 r POS register 1 High adapter ID byte

0102 r/w POS register 2 option select data byte 1
bit 0 is card enable (CDEN)

0103 r/w POS register 3 option select data byte 2
0104 r/w POS register 4 option select data byte 3
0105 r/w POS register 5 option select data byte 4
bit 7 channel active (-CHCK)
bit 6 channel status

0106 r/w POS register 6 Low subaddress extension
0107 r/w POS register 7 High subaddress extension

-------------------------------------------------------------------------------
0108-010F ---- 8 digit LED info panel on IBM PS/2

010F w leftmost character on display
010E w second character
.... w
0108 w eighth character

-------------------------------------------------------------------------------
0130-013F ---- CompaQ SCSI adapter. alternate address at 0330

-------------------------------------------------------------------------------
0130-0133 ---- Adaptec 154xB/154xC SCSI adapter.
alternate address at 0134, 0230, 0234, 0330 and 0334

-------------------------------------------------------------------------------
0134-0137 ---- Adaptec 154xB/154xC SCSI adapter.
alternate address at 0130, 0230, 0234, 0330 and 0334

-------------------------------------------------------------------------------
0138-013F ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
0140-014F ---- SCSI (alternate Small Computer System Interface) adapter
(1st at 0340-034F)

-------------------------------------------------------------------------------
0140-0157 ---- RTC (alternate Real Time Clock for XT) (1st at 0340-0357)

-------------------------------------------------------------------------------
015F ---- ARTEC Handyscanner A400Z. alternate address at 35F.

-------------------------------------------------------------------------------
0170-0177 ---- HDC 2 (2nd Fixed Disk Controller) same as 01Fx (ISA, EISA)

-------------------------------------------------------------------------------
0178-0179 ---- Power Management

0178 w index selection for data port
0179 r/w power management data

-------------------------------------------------------------------------------
0178-017F ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
01E8-01EF ---- System Control. Laptop chipset: Headland HL21 & Acer M5105

01ED r/w select internal register. Data to/from 01EF
01EE r
01EF r/w reg.
5 = 1000xxxx for low CPU clock speed (4MHz on Morse/Mitac)
= 0xxxxxxx for high CPU clock speed (16MHz on Morse/Mitac)

-------------------------------------------------------------------------------
01F0-01F7 ---- HDC 1 (1st Fixed Disk Controller) same as 017x (ISA, EISA)

01F0 r/w data register

01F1 r error register
diagnostic mode errors:
bit 7-3 reserved
bit 2-1 = 001 no error detected
= 010 formatter device error
= 011 sector buffer error
= 100 ECC circuitry error
= 101 controlling microprocessor error
operation mode:
bit 7 = 1 bad block detected
= 0 block OK
bit 6 = 1 uncorrectable ECC error
= 0 no error
bit 5 reserved
bit 4 = 1 ID found
= 0 ID not found
bit 3 reserved
bit 2 = 1 command completed
= 0 command aborted
bit 1 = 1 track 000 not found
= 0 track 000 found
bit 0 = 1 DAM not found
= 0 DAM found (CP-3022 always 0)

01F1 w WPC/4 (Write Precompensation Cylinder divided by 4)

01F2 r/w sector count
01F3 r/w sector number
01F4 r/w cylinder low
01F5 r/w cylinder high

01F6 r/w drive/head
bit 7 = 1
bit 6 = 0
bit 5 = 1
bit 4 = 0 drive 0 select
= 1 drive 1 select
bit 3-0 head select bits

01F7 r status register
bit 7 = 1 controller is executing a command
bit 6 = 1 drive is ready
bit 5 = 1 write fault
bit 4 = 1 seek complete
bit 3 = 1 sector buffer requires servicing
bit 2 = 1 disk data read successfully corrected
bit 1 = 1 index - set to 1 each disk revolution
bit 0 = 1 previous command ended in an error

01F7 w command register
commands:
98 E5 check power mode (IDE)
90 execute drive diagnostics
50 format track
EC identify drive (IDE)
97 E3 idle (IDE)
95 E1 idle immediate (IDE)
91 initialize drive parameters
1x recalibrate
E4 read buffer (IDE)
C8 read DMA with retry (IDE)
C9 read DMA without retry (IDE)
C4 read multiplec (IDE)
20 read sectors with retry
21 read sectors without retry
22 read long with retry
23 read long without retry
40 read verify sectors with retry
41 read verify sectors without retry
7x seek
EF set features (IDE)
C6 set multiple mode (IDE)
99 E6 set sleep mode (IDE)
96 E2 standby (IDE)
94 E0 standby immediate (IDE)
E8 write buffer (IDE)
CA write DMA with retry (IDE)
CB write DMA with retry (IDE)
C5 write multiple (IDE)
E9 write same (IDE)
30 write sectors with retry
31 write sectors without retry
32 write long with retry
33 write long without retry
3C write verify (IDE)
9A vendor unique (IDE)
C0-C3 vendor unique (IDE)
8x vendor unique (IDE)
F0-F4 EATA standard (IDE)
F5-FF vendor unique (IDE)

-------------------------------------------------------------------------------
01F8 ---- ???

01F8 r/w ???
bit 0: A20 gate control (set = A20 enabled, clear = disabled)

-------------------------------------------------------------------------------
01F9-01FF ---- PC radio by CoZet Info Systems
The I/O address range is dipswitch selectable from:
038-03F and 0B0-0BF
078-07F and 0F0-0FF
138-13F and 1B0-1BF
178-17F and 1F0-1FF
238-23F and 2B0-2BF
278-27F and 2F0-2FF
338-33F and 3B0-3BF
378-37F and 3F0-3FF
All of these addresses show a readout of FF in initial state.
Once started, all of the addresses show FB, whatever might
happen.

-------------------------------------------------------------------------------
0200-020F ---- Game port reserved I/O address space
0200-0207 ---- Game port, eight identical addresses on some boards

0201 r read joystick position and status
bit 7 status B joystick button 2 / D paddle button
bit 6 status B joystick button 1 / C paddle button
bit 5 status A joystick button 2 / B paddle button
bit 4 status A joystick button 1 / A paddle button
bit 3 B joystick Y coordinate / D paddle coordinate
bit 2 B joystick X coordinate / C paddle coordinate
bit 1 A joystick Y coordinate / B paddle coordinate
bit 0 A joystick X coordinate / A paddle coordinate

w fire joysticks four one-shots

-------------------------------------------------------------------------------
0200-02FF ---- Sunshine uPW48, programmer for EPROM version CPU's 8748/8749
(4 bit DIP switch installable in the range 20x-2Fx)
0200-0203 adresses of the 8255 on the uPW48
0208-020B adresses of ??? on the uPW48 (all showing zeros)


-------------------------------------------------------------------------------
0210-0217 ---- Expansion unit (XT)

0210 w latch expansion bus data
r verify expansion bus data
0211 w clear wait, test latch
r High byte data address
0212 r Low byte data address
0213 w 0=enable, 1=disable expansion unit
0214 w latch data (receiver card port)
r read data (receiver card port)
0215 r High byte of address, then Low byte (receiver card port)

------------------------------------------------------------------------------
0220-0223 ---- Sound Blaster / Adlib port

0220 r/w Left speaker -- Status / Address port
0221 w Left speaker -- Data port
0222 r/w Right speaker -- Status / Address port
Address:
01 -- Enable waveform control
02 -- Timer #1 data
03 -- Timer #2 data
04 -- Timer control flags
08 -- Speech synthesis mode
20-35 -- Amplitude Modulation / Vibrato
40-55 -- Level key scaling / Total level
60-75 -- Attack / Decay rate
80-95 -- Sustain / Release rate
A0-B8 -- Octave / Frequency Number
C0-C8 -- Feedback / Algorithm
E0-F5 -- Waveform Selection
0223 w Right speaker -- Data port

SeeAlso: 0388-0389

-------------------------------------------------------------------------------
0220-0227 ---- Soundblaster PRO and SSB 16 ASP

-------------------------------------------------------------------------------
0220-022F ---- Soundblaster PRO 2.0

-------------------------------------------------------------------------------
0220-022F ---- Soundblaster PRO 4.0
0220 r left FM status port
0220 w left FM music register address port (index)
0221 r/w left FM music data port
0222 r right FM status port
0222 w right FM music register address port (index)
0223 r/w right FM music data port
0224 w mixer register address port (index)
0225 r/w mixer data port
0226 w DSP reset
0228 r FM music status port
0228 w FM music register address port (index)
0229 w FM music data port
022A r DSP read data (voice I/O and Midi)
022C w DSP write data / write command
022C r DSP write buffer status (bit 7)
022E r DSP data available status (bit 7)

The FM music is accessible on 0388/0389 for compatibility.

-------------------------------------------------------------------------------
0230-0233 ---- Adaptec 154xB/154xC SCSI adapter.
alternate address at 0130, 0134, 0230, 0330 and 0334

-------------------------------------------------------------------------------
0234-0237 ---- Adaptec 154xB/154xC SCSI adapter.
alternate address at 0130, 0134, 0230, 0330 and 0334

-------------------------------------------------------------------------------
0240-024F ---- Gravis Ultra Sound by Advanced Gravis
The I/O address range is dipswitch selectable from:
0200-020F and 0300-030F
0210-021F and 0310-031F
0220-022F and 0320-032F
0230-023F and 0330-033F
0240-024F and 0340-034F
0250-025F and 0350-035F
0260-026F and 0360-036F
0270-027F and 0370-037F

0240 w Mix Control register
bit 6 Control Register Select (see 024B)
bit 5 Enable MIDI Loopback
bit 4 Combine GF1 IRQ with MIDI IRQ
bit 3 Enable Latches
bit 2 Enable MIC IN
bit 1 Disable LINE OUT
bit 0 Disable LINE IN
0241 r Read Data
w Trigger Timer
0246 r IRQ Status Register
bit 7 DMA TC IRQ
bit 6 Volume Ramp IRQ
bit 5 WaveTable IRQ
bit 3 Timer 2 IRQ
bit 2 Timer 1 IRQ
bit 1 MIDI Receive IRQ
bit 0 MIDI Transmit IRQ
0248 r/w Timer Control Reg
Same a ADLIB Board (look at 0200)
0249 w Timer Data
bit 7 Reset Timr IRQ
bit 6 Mask Timer 1
bit 5 Mask Timer 2
bit 1 Timer 2 Start
bit 0 Timer 1 Start
024B w IRQ Control Register (0240 bit 6 = 1)
bit 6 Combine Both IRQ
bit 5-3 MIDI IRQ Selector
= 000 No IRQ
= 001 IRQ 2
= 010 IRQ 5
= 011 IRQ 3
= 100 IRQ 7
= 101 IRQ 11
= 110 IRQ 12
= 111 IRQ 15
bit 2-0 GF1 IRQ Selector
= 000 No IRQ
= 001 IRQ 2
= 010 IRQ 5
= 011 IRQ 3
= 100 IRQ 7
= 101 IRQ 11
= 110 IRQ 12
= 111 IRQ 15
DMA Control Register (0240 bit 6 = 0)
bit 6 Combine Both IRQ
bit 5-3 DMA Select Register 2
= 000 No DMA
= 001 DMA 1
= 010 DMA 3
= 011 DMA 5
= 100 DMA 6
= 101 DMA 7
bit 2-0 DMA Select Register 1
= 000 No DMA
= 001 DMA 1
= 010 DMA 3
= 011 DMA 5
= 100 DMA 6
= 101 DMA 7
024F r/w Register Controls (rev 3.4+)

SeeAlso: 0340-034F, 0746
-------------------------------------------------------------------------------
0240-0257 ---- RTC (alternate Real Time Clock for XT) (1st at 0340-0357)
(used by TIMER.COM v1.2 which is the 'standard' timer program)

-------------------------------------------------------------------------------
0258-025F ---- Intel Above Board

-------------------------------------------------------------------------------
0278-027E ---- parallel printer port, same as 0378 and 03BC

0278 w data port
0279 r/w status port
027A r/w control port

-------------------------------------------------------------------------------
02A0-02A7 ---- Sunshine EW-901BN, EW-904BN
EPROM writer card (release 1986) for EPROMs up to 27512
02A0-02A3 adresses of the 8255 on the EW-90xBN


-------------------------------------------------------------------------------
02A2-02A3 ---- MSM58321RS clock

-------------------------------------------------------------------------------
02B0-02BF ---- Trantor SCSI adapter

-------------------------------------------------------------------------------
02B0-02DF ---- alternate EGA, primary EGA at 03C0

-------------------------------------------------------------------------------
02C0-02Cx ---- AST-clock

-------------------------------------------------------------------------------
02E0-02EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)
(GAB 0 on XT)
02E1 GPIB (adapter 0)
02E2
02E3

-------------------------------------------------------------------------------
02E0-02EF ---- data aquisition (AT)

02E2 data aquisition (adapter 0)
02E3 data aquisition (adapter 0)

-------------------------------------------------------------------------------
02E8 ---- S3 86C928 video controller (ELSA Winner 1000)

-------------------------------------------------------------------------------
02E8-02EF ---- serial port, same as 02F8, 03E8 and 03F8

-------------------------------------------------------------------------------
02E8-02EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

02E8 r display status
02E8 w horizontal total
02EA w DAC mask
02EB w DAC read index
02EC w DAC write index
02ED w DAC data

-------------------------------------------------------------------------------
02EA ---- S3 86C928 video controller (ELSA Winner 1000)

-------------------------------------------------------------------------------
02F8-02FF ---- serial port, same as 02E8, 03E8 and 03F8

02F8 w transmitter holding register
02F8 r receiver buffer register
r/w divisor latch, low byte when DLAB=1
02F9 r/w divisor latch, high byte when DLAB=1
r/w interrupt enable register when DLAB=0
02FA r interrupt identification register
02FB r/w line control register
02FC r/w modem control register
02FD r line status register
02FF r/w scratch register

-------------------------------------------------------------------------------
0300 ---- Award POST Diagnostic

-------------------------------------------------------------------------------
0300-0301 ---- Soundblaster 16 ASP MPU-Midi

-------------------------------------------------------------------------------
0300-0303 ---- Panasonic 52x CD-ROM SCSI Miniport
Alternate addresses at 0320, 0340, 0360, and 0380

-------------------------------------------------------------------------------
0300-030F ---- Philips CD-ROM player CM50

-------------------------------------------------------------------------------
0300-030F ---- CompaQ Tape drive adapter. alternate address at 0100

-------------------------------------------------------------------------------
0300-031F ---- prototype cards
Periscope hardware debugger

-------------------------------------------------------------------------------
0310-031F ---- Philips CD-ROM player CM50

-------------------------------------------------------------------------------
0320-0323 ---- XT HDC 1 (Hard Disk Controller)

0320 r/w data register

0321 w reset controller
r read controller hardware status
bit 7-6 = 0
bit 5 logical unit number
bit 4-2 = 0
bit 1 = 0 no error
bit 0 = 0

0322 r read DIPswitch setting on XT controller card
w generate controller-select pulse
0323 w write pattern to DMA and INT mask register

0324-0327 ---- XT HDC 2 (Hard Disk Controller)
0328-032B ---- XT HDC 3 (Hard Disk Controller)
032C-032F ---- XT HDC 4 (Hard Disk Controller)

-------------------------------------------------------------------------------
0330-0331 ---- MIDI interface

-------------------------------------------------------------------------------
0330-0333 ---- Adaptec 154xB/154xC SCSI adapter. default address.
alternate address at 0130, 0134, 0230, 0234 and 0334

-------------------------------------------------------------------------------
0330-033F ---- CompaQ SCSI adapter. alternate address at 0130

-------------------------------------------------------------------------------
0330-033F ---- Philips CD-ROM player CM50

-------------------------------------------------------------------------------
0334-0337 ---- Adaptec 154xB/154xC SCSI adapter.
alternate address at 0130, 0134, 0230, 0234 and 0330

-------------------------------------------------------------------------------
0338 ---- AdLib soundblaster card

-------------------------------------------------------------------------------
0340-034F ---- Philips CD-ROM player CM50

-------------------------------------------------------------------------------
0340-034F ---- SCSI (1st Small Computer System Interface) adapter
(alternate at 0140-014F)

-------------------------------------------------------------------------------
0340-034F ---- Gravis Ultra Sound by Advanced Gravis
The I/O address range is dipswitch selectable from:
0200-020F and 0300-030F
0210-021F and 0310-031F
0220-022F and 0320-032F
0230-023F and 0330-033F
0240-024F and 0340-034F
0250-025F and 0350-035F
0260-026F and 0360-036F
0270-027F and 0370-037F
0340 w MIDI Control
bit 7 Receive IRQ (1 = enabled)
bit 5-6 Xmit IRQ
bit 0-1 Master Reset (1 = enabled)
r MIDI Status
bit 7 Interrupt pending
bit 5 Overrun Error
bit 4 Framing Error
bit 1 Transmit Register Empty
bit 0 Receive Register Empty
0341 w MIDI Transmit Data
r MIDI Receive Data
0342 r/w GF1 Page Register / Voice Select
0343 r/w GF1/Global Register Select
Global Registers, NOT voice specific:
41 r/w DRAM DMA Control
bit 7 Invert MSB
bit 6 Data Size (8/16 bits)
bit 5 DMA Pending
bit 3-4 DMA Rate Divider
bit 2 DMA Channel Width (8/16 bits)
bit 1 DMA Direction (1 = read)
bit 0 DMA Enable
42 w DMA Start Address
bits 15-0 DMA Address Lines 19-4
43 w DRAM I/O Address LOW
44 w DRAM I/O Address HIGH
bits 0-3 Upper 4 Address Lines
45 r/w Timer Control
bit 3 Enable Timer 2
bit 2 Enable Timer 1
46 w Timer 1 Count (granularity of 80 micro sec)
47 w Timer 2 Count (granulatity of 320 micro sec)
48 w Sampling Frequency
rate = 9878400 / (16 * (FREQ + 2))
49 r/w Sampling Control
bit 7 Invert MSB
bit 6 DMA IRQ pending
bit 5 DMA IRQ enable
bit 2 DMA width (8/16 bits)
bit 1 Mode (mone/stereo)
bit 0 Start Sampling
4B w Joystick Trim DAC
4C r/w RESET
bit 2 GF1 Master IRQ Enable
bit 1 DAC Enable
bit 0 Master Reset
Voice specific registers:
00 w Voice Control
bit 7 IRQ pending
bit 6 Direction
bit 5 Enable WAVE IRQ
bit 4 Enable bi-directional Looping
bit 3 Enable Looping
bit 2 Size data (8/16 bits)
bit 1 Stop Voice
bit 0 Voice Stopped
01 w Frequency Control
bit 15-10 Integer Portion
bit 9-1 Fractional Portion
02 w Start Address HIGH
bit 12-0 Address Lines 19-7
03 w Start Address LOW
bit 15-9 Address Lines 6-0
bit 8-5 Fractional Part of Start Address
04 w End Address HIGH
bit 12-0 Address Lines 19-7
05 w End Address LOW
bit 15-9 Address Lines 6-0
bit 8-5 Fractional Part of End Address
06 w Volume Ramp Rate
bit 5-0 Amount added
bit 7-6 Rate
07 w Volume Ramp Start
bit 7-4 Exponent
bit 3-0 Mantissa
08 w Volume Ramp End
bit 7-4 Exponent
bit 3-0 Mantissa
09 w Current Volume
bit 15-12 Exponent
bit 11-4 Mantissa
0A w Current Address HIGH
bit 12-0 Address Lines 19-7
0B w Current Address LOW
bit 15-9 Address Lines 6-0
bit 8-0 Fractional Position
0C w Pan Position
bit 3-0 Pan Postion
0D w Volume Control
bit 7 IRQ Pending
bit 6 Direction
bit 5 Enable Volume Ramp IRQ
bit 4 Enable bi-directional Looping
bit 3 Enable Looping
bit 2 Rollover Condition
bit 1 Stop Ramp
bit 0 Ramp Stopped
0E w Active Voices
bit 5-0 #Voices -1 (allowed 13 - 31)
0F w IRQ Source Register
bit 7 WaveTable IRQ pending
bit 6 Volume Ramp IRQ pending
bit 4-0 Voice Number
80 r Voice Control (see 00)
81 r Frequency Control (see 01)
82 r Start Address HIGH (see 02)
83 r Start Address LOW (see 03)
84 r End Address HIGH (see 04)
85 r End Address LOW (see 05)
86 r Volume Ramp Rate (see 06)
87 r Volume Ramp Start (see 07)
88 r Volume Ramp End (see 08)
89 r Current Volume (see 09)
8A r Current Address HIGH (see 0A)
8B r Current Address LOW (see 0B)
8C r Pan Position (see 0C)
8D r Volume Control (see 0D)
8E r Active Voices (see 0E)
8F r IRQ Status (see 0F)
0344 r/w GF1/Global Data Low Byte (16 bits)
0345 r/w GF1/Global Data High Byte (8 bits)
0346 w Mixer Data Port
0347 r/w GF1 DRAM
Direct Read Write at Loction pointed with regs 43 and 44

SeeAlso: 0240-024F, 0746
-------------------------------------------------------------------------------
0340-0357 ---- RTC (1st Real Time Clock for XT), (alternate at 0240-0257)
(used by TIMER.COM v1.2 which is the 'standard' timer program)

0340 r/w 0.01 seconds 0-99
0341 r/w 0.1 seconds 0-99
0342 r/w seconds 0-59
0343 r/w minutes 0-59
0343 r/w hours 0-23
0345 r/w day of week 1-7
0346 r/w day of month 1-31
0347 r/w month 1-12
0348
0349 r/w year 0-99
034A
034B
034C
034D
034E
034F
0350 r status?
0351
0352
0353
0354 r status?
0355
0356
0357

-------------------------------------------------------------------------------
0348-0357 ---- DCA 3278

-------------------------------------------------------------------------------
034C-034F ---- Gravis UltraMax by Advanced Gravis
The I/O address range is dipswitch selectable from:
0200-020F and 0300-030F
0210-021F and 0310-031F
0220-022F and 0320-032F
0230-023F and 0330-033F
0240-024F and 0340-034F
0250-025F and 0350-035F
0260-026F and 0360-036F
0270-027F and 0370-037F

-------------------------------------------------------------------------------
035A-035B ---- Adaptec AH1520 jumper settings

035A r bit 7: SCSI parity disabled
bits 6-5: DMA channel
(00 = channel 0, 01 = 5, 10 = 6, 11 = 7)
bits 4-3: IRQ number
(00 = IRQ9, 01 = IRQ10, 10 = IRQ11, 11 = IRQ12)
bits 2-0: SCSI ID
035B r bit 7: DMA transfer mode (clear for PIO)
bit 6: boot enabled
bits 5-4: boot type
00 ???
01 boot from floppy
10 print configured options
11 boot from hard disk
bit 3: enable sync negotiation
bit 2: enable target disconnection
bits 1-0: unused???

-------------------------------------------------------------------------------
035F ---- ARTEC Handyscanner A400Z. alternate address at 15F.

-------------------------------------------------------------------------------
0360-036F ---- PC network (AT)
0360-0367 ---- PC network (XT only)

-------------------------------------------------------------------------------
0360-036F ---- National Semiconductor DP8390(1)C/NS3249C network chipset
Note: cards based on this IEEE 802.3 networking chipset can use any range
of 16 consecutive addresses, and provide a total of four pages of
sixteen register

Page 0 r w

00 Command reg. CR Command reg. CR
01 current local DMA address 0 CLDA0 page start reg. PSTART
02 current local DMA address 1 CLDA1 page stop reg. PSTOP
03 boundary pointer BNRY boundary pointer BNRY
04 transmit status reg. TSR Tx page start address TPSR
05 number of collisions reg. NCR Tx byte count reg.0 TBCR0
06 FIFO Tx byte count reg.1 TBCR1
07 interrupt status reg. ISR interrupt status reg. ISR
08 current remote DMA address 0 CRDA0 remote start addr.reg.0 RSAR0
09 current remote DMA address 1 CRDA1 remote start addr.reg.1 RSAR1
0A reserved remote byte count reg.0 RBCR0
0B reserved remote byte count reg.1 RBCR1
0C receive status reg. RSR Rx configuration reg. RCR
0D tally counter 0 (frame errors) CNTR0 Tx configuration reg. TCR
0E tally counter 1 (CRC errors) CNTR1 data configuration reg. DCR
0F tally counter 2 (missed pkt) CNTR2 interrupt mask reg. IMR

Page 1 r/w

00 Command CR
01 physical address reg.0 PAR0
02 physical address reg.1 PAR1
03 physical address reg.2 PAR2
04 physical address reg.3 PAR3
05 physical address reg.4 PAR4
06 physical address reg.5 PAR5
07 current page reg. CURR
08 multicast address reg.0 MAR0
09 multicast address reg.1 MAR1
0A multicast address reg.2 MAR2
0B multicast address reg.3 MAR3
0C multicast address reg.4 MAR4
0D multicast address reg.5 MAR5
0E multicast address reg.6 MAR6
0F multicast address reg.7 MAR7

Page 2 r w
diagnostics page - should never be modfied under normal operation.

00 Command CR Command CR
01 page start reg. PSTART current local DMA addr.0 CLDA0
02 page stop reg. BPSTOP current local DMA addr.1 CLDA1
03 remote next packet pointer remote next packet pointer
04 Tx page start address TPSR reserved
05 local next packet pointer local next packet pointer
06 address counter (upper) address counter (upper)
07 address counter (lower) address counter (lower)
08 reserved reserved
09 reserved reserved
0A reserved reserved
0B reserved reserved
0C Rx configuration reg. RCR reserved
0D Tx configuration reg. TCR reserved
0E data configuration reg. DCR reserved
0F interrupt mask reg. IMR reserved

Page 3 r w
Test Page - should never be modified !

00 Command CR Command CR

bit0=1 software reset command. 1=offline 0=online
bit1=0 activate NIC after reset command
bit2=1 start transmision of a packet
bit3-5 remote DMA command
000 not allowed
001 remote read
010 remote write
011 send packet
1xx abort/complete rmote DMA
bit 6,7 page select
00 register page 0
01 register page 1
10 register page 2
11 register page 3

-------------------------------------------------------------------------------
0370-0377 ---- FDC 2 (2nd Floppy Disk Controller) first FDC at 03F0
(8272, 8272A, NEC765)
(82072, 82077AA for perpendicular recording at 2.8Mb)

0370 r diskette Extra High Density controller board jumpers (AT)
0370 r diskette controller status A (PS/2, PS/2 model 30)
0371 r diskette controller status B (PS/2, PS/2 model 30)
0372 w diskette controller DOR (Digital Output Register)
0374 r diskette controller main status register
0374 w diskette controller datarate select register
0375 r/w diskette controller command/data register
0376 r/w (2nd FIXED disk controller data register)
0377 r diskette controller DIR (Digital Input Register)
0377 w select register for diskette data transfer rate

-------------------------------------------------------------------------------
0378-037A ---- parallel printer port, same as 0278 and 03BC

0378 w data port
0379 r/w status port
037A r/w control port

-------------------------------------------------------------------------------
0380-038F ---- 2nd Binary Synchronous Data Link Control adapter (see 03A0)

0380 r/w on board 8255 port A, internal/external sense
0381 r/w on board 8255 port B, external modem interface
0382 r/w on board 8255 port C, internal control and gating
0383 r/w on board 8255 mode register
0384 r/w on board 8253 channel square wave generator
0385 r/w on board 8253 channel 1 inactivity time-out
0386 r/w on board 8253 channel 2 inactivity time-out
0387 r/w on board 8253 mode register
0388 r/w on board 8273 read: status write: command
0389 r/w on board 8273 read: response write: parameter
038A r/w on board 8273 transmit interrupt status
038B r/w on board 8273 receiver interrupt status
038C r/w on board 8273 data

------------------------------------------------------------------------------
0388-0389 ---- Sound Blaster / Adlib port

0388 r/w Both Speakers -- Status / Address port
Address:
01 -- Enable waveform control
02 -- Timer #1 data
03 -- Timer #2 data
04 -- Timer control flags
08 -- Speech synthesis mode
20-35 -- Amplitude Modulation / Vibrato
40-55 -- Level key scaling / Total level
60-75 -- Attack / Decay rate
80-95 -- Sustain / Release rate
A0-B8 -- Octave / Frequency Number
C0-C8 -- Feedback / Algorithm
E0-F5 -- Waveform Selection
0389 w Data port

SeeAlso: 0220-0223

-------------------------------------------------------------------------------
0388-0389 ---- Soundblaster PRO FM-Chip
0388-038B ---- Soundblaster 16 ASP FM-Chip

-------------------------------------------------------------------------------
0390-0397 ---- Sunshine EW-901B, EW-904B
EPROM writer card for EPROMs up to 27512
0390-0393 adresses of the 8255 on the EW-90xB

-------------------------------------------------------------------------------
0390-039F ---- Cluster adapter (AT)

0390-0393 (adapter 0) (XT)

-------------------------------------------------------------------------------
03A0-03AF ---- 1st SDLC (Binary Synchronous Data Link Control adapter)

03A0 r/w on board 8255 port A, internal/external sense
03A1 r/w on board 8255 port B, external modem interface
03A2 r/w on board 8255 port C, internal control and gating
03A3 r/w on board 8255 mode register
03A4 r/w on board 8253 counter 0 unused
03A5 r/w on board 8253 channel 1 inactivity time-out
03A6 r/w on board 8253 channel 2 inactivity time-out
03A7 r/w on board 8253 mode register
03A8 r/w on board 8251 data
03A9 r/w on board 8251 command/mode/status register

-------------------------------------------------------------------------------
03B0-03BF ---- MDA (Monochrome Display Adapter based on 6845)

03B0 same as 03B4
03B1 same as 03B5
03B2 same as 03B4
03B3 same as 03B5
03B4 w MDA CRT index register (EGA/VGA)
selects which register (0-11h) is to be accessed through 3B5
03B5 r/w MDA CRT data register (EGA/VGA)
selected by port 3B4. registers C-F may be read
00 horizontal total
01 horizontal displayed
02 horizontal sync position
03 horizontal sync pulse width
04 vertical total
05 vertical displayed
06 vertical sync position
07 vertical sunc pulse width
08 interlace mode
09 maximum scan lines
0A cursor start
0B cursor end
0C start address high
0D start address low
0E cursor location high
0F cursor location low
10 light pen high
11 light pen low
03B6 same as 03B4
03B7 same as 03B5
03B8 r/w MDA mode control register
bit 7 not used
bit 6 not used
bit 5 enable blink
bit 4 not used
bit 3 video enable
bit 2 not used
bit 1 not used
bit 0 high resolution mode

03B9 reserved for color select register on color adapter

03BA r CRT status register EGA/VGA: input status 1 register
bit 7 (MSD says) if this bit changes within 8000h reads then
bit 6-4 = 000 = adapter is Hercules or compatible
001 = adapter is Hercules+
101 = adapter is Hercules InColor
else: adapter is unknown
bit 3 black/white video
bit 2-1 reserved
bit 0 horizontal drive

03BA w EGA/VGA feature control register

03BB reserved for light pen strobe reset

-------------------------------------------------------------------------------
03BC-03BF ---- parallel printer port, same as 0278 and 0378

03BC w data port
03BD r/w status port
bit 7 = 0 busy
bit 6 = 0 acknowledge
bit 5 = 1 out of paper
bit 4 = 1 printer is selected
bit 3 = 0 error
bit 2 = 0 IRQ has occurred
bit 1-0 reserved

03BE r/w control port
bit 7-5 reserved
bit 4 = 1 enable IRQ
bit 3 = 1 select printer
bit 2 = 0 initialize printer
bit 1 = 1 automatic line feed
bit 0 = 1 strobe

-------------------------------------------------------------------------------
03BF r/w Hercules configuration switch register
bit 7-2
bit 1 = 0 disables upper 32K of graphics mode buffer
1 enables upper 32K of graphics mode buffer
bit 0 = 0 prevents graphics mode
1 allows graphics mode

-------------------------------------------------------------------------------
03C0-03C7 ---- Sunshine EW-901, EW-901A, EW-904, EW-904A
EPROM writer card for EPROMs up to 27512
03C0-03C3 adresses of the 8255 on the EW-90x

-------------------------------------------------------------------------------
03C0-03CF ---- EGA (1st Enhanced Graphics Adapter) alternate at 02C0

03C0 (r)/w EGA VGA ATC index/data register
03C1 r VGA other attribute register
03C2 r EGA VGA input status 0 register
w VGA miscellaneous output register
03C3 r/w VGA video subsystem enable (see also port 46E8h)
for IBM, motherboard VGA only
03C4 w EGA TS index register
r/w VGA sequencer index register
03C5 w EGA TS data register
r/w VGA other sequencer register
03C6 r/w VGA PEL mask register
03C7 r/w VGA PEL address read mode
r VGA DAC state register
03C8 r/w VGA PEL address write mode
03C9 r/w VGA PEL data register
03CA w EGA graphics 2 position register
r VGA feature control register
03CC w EGA graphics 1 position register
r VGA miscellaneous output register
03CE w EGA GDC index register
r/w VGA graphics address register
03CF w EGA GDC data register
r/w VGA other graphics register

-------------------------------------------------------------------------------
03CE-03CF ---- Compaq Qvision - Functionality Level

03CE w graphics address register (index for next port)
03CF r/w other graphics register
Index
0Ch r controller version
2Fh Advanced VGA
37h early QVision 1024
71h QVision 1280 or later QVision 1024
0Dh extended controller version
0Eh extended controller capabilities
0Fh environment info
54h available memory
55h phase-locked-loop clock
56h-57h controller capabilities

-------------------------------------------------------------------------------
03D0-03DF ---- CGA (Color Graphics Adapter)

03D0 same as 03D4
03D1 same as 03D5
03D2 same as 03D4
03D3 same as 03D5
03D4 w CRT (6845) index register (EGA/VGA)
selects which register (0-11h) is to be accessed through 3B5
03D5 w CRT (6845) data register (EGA/VGA)
selected by port 3B4. registers C-F may be read
(for registers see at 3B5)
03D6 same as 03D4
(under OS/2, reads return 0 if full-screen DOS session,
nonzero if windowed DOS session)
03D7 same as 03D5
03D8 r/w CGA mode control register (except PCjr)
bit 7-6 not used
bit 5 = 1 blink enabled
bit 4 = 1 640*200 graphics mode
bit 3 = 1 video enabled
bit 2 = 1 monochrome signal
bit 1 = 0 text mode
= 1 320*200 graphics mode
bit 0 = 0 40*25 text mode
= 1 80*25 text mode

03D9 r/w CGA palette register
bit 7-6 not used
bit 5 = 0 active color set: red, green brown
= 1 active color set: cyan, magenta, white
bit 4 intense colors in graphics, background colors text
bit 3 intense border in 40*25, intense background in
320*200, intense foreground in 640*200
bit 2 red border in 40*25, red background in 320*200,
red foreground in 640*200
bit 1 green border in 40*25, green background in
320*200, green foreground in 640*200
bit 0 blue border in 40*25, blue background in 320*200,
blue foreground in 640*200

03DA r CGA status register EGA/VGA: input status 1 register
bit 7-4 not used
bit 3 = 1 in vertical retrace
bit 2 = 1 light pen switch is off
bit 1 = 1 positive edge from light pen has set trigger
bit 0 = 0 do not use memory
= 1 memory access without interfering with display

03DA w EGA/VGA feature control register

03DB w clear light pen latch
03DC r/w preset light pen latch

03DF CRT/CPU page register (PCjr only)

-------------------------------------------------------------------------------
03E8-03EF ---- serial port, same as 02E8, 02F8 and 03F8

-------------------------------------------------------------------------------
03F0-03F7 ---- FDC 1 (1st Floppy Disk Controller) second FDC at 0370
(8272, 8272A, NEC765)
(82072, 82077AA for perpendicular recording at 2.8Mb)

03F0 r diskette EHD controller board jumper settings (82072AA)
bit 7-6 drive 3
bit 5-4 drive 2
bit 3-2 drive 1
bit 1-0 drive 0
= 00 1.2Mb
= 01 720Kb
= 10 2.8Mb
= 11 1.4Mb

03F0 r diskette controller status A (PS/2)
bit 7 interrupt pending
bit 6 -DRV2 second drive installed
bit 5 step
bit 4 -track 0
bit 3 head 1 select
bit 2 -index
bit 1 -write protect
bit 0 +direction

03F0 r diskette controller status A (PS/2 model 30)
bit 7 interrupt pending
bit 6 DRQ
bit 5 step F/F
bit 4 -track 0
bit 3 head 1 select
bit 2 +index
bit 1 +write protect
bit 0 -direction

03F1 r diskette controller status B (PS/2)
bit 7-6 =1 reserved
bit 5 drive select (0=A:, 1=B:)
bit 4 write data
bit 3 read data
bit 2 write enable
bit 1 motor enable 1
bit 0 motor enable 0

03F1 r diskette controller status B (PS/2 model 30)
bit 7 -DRV2 second drive installed
bit 6 -DS1
bit 5 -DS0
bit 4 write data F/F
bit 3 read data F/F
bit 2 write enable F/F
bit 1 -DS3
bit 0 -DS2

03F2 w diskette controller DOR (Digital Output Register)
bit 7-6 reserved on PS/2
bit 7 = 1 drive 3 motor enable
bit 6 = 1 drive 2 motor enable
bit 5 = 1 drive 1 motor enable
bit 4 = 1 drive 0 motor enable
bit 3 = 1 diskette DMA enable (reserved PS/2)
bit 2 = 1 FDC enable (controller reset)
= 0 hold FDC at reset
bit 1-0 drive select (0=A 1=B ..)

03F3 tape drive register (on the 82077AA)
bit 7-2 reserved, tri-state
bit 1-0 tape select
= 00 none, drive 0 cannot be a tape drive.
= 01 drive1
= 10 drive2
= 11 drive3

03F4 r diskette controller main status register
bit 7 = 1 RQM data register is ready
0 no access is permitted
bit 6 = 1 transfer is from controller to system
0 transfer is from system to controller
bit 5 = 1 non-DMA mode
bit 4 = 1 diskette controller is busy
bit 3 = 1 drive 3 busy (reserved on PS/2)
bit 2 = 1 drive 2 busy (reserved on PS/2)
bit 1 = 1 drive 1 busy (= drive is in seek mode)
bit 0 = 1 drive 0 busy (= drive is in seek mode)
Note: in non-DMA mode, all data transfers occur through
port 03F5h and the status registers (bit 5 here
indicates data read/write rather than than
command/status read/write)

03F4 w diskette controller data rate select register
bit 7-2 reserved on 8272
bit 7 = 1 software reset (self clearing) 82072/82077AA
bit 6 = 1 power down 82072/82077AA
bit 5 = 0 reserved on 8272 and 82077AA
PLL select bit on 82072
bit 4-2 write precompensation value, 000 default
bit 1-0 data rate select
= 00 500 Kb/S MFM 250 Kb/S FM
= 01 300 Kb/S MFM 150 Kb/S FM
= 10 250 Kb/S MFM 125 Kb/S FM
= 11 1Mb/S MFM illegal FM on 8207x

03F5 r diskette command/data register 0 (ST0)
bit 7-6 last command status
= 00 command terminated successfully
= 01 command terminated abnormally
= 10 invalid command
= 11 terminated abnormally by change in ready signal
bit 5 = 1 seek completed
bit 4 = 1 equipment check occurred after error
bit 3 = 1 not ready
bit 2 = 1 head number at interrupt
bit 1-0 = 1 unit select (0=A 1=B .. )
(on PS/2 01=A 10=B)

status register 1 (ST1)
bit 7 end of cylinder; sector# greater then sectors/track
bit 6 = 0
bit 5 = 1 CRC error in ID or data field
bit 4 = 1 overrun
bit 3 = 0
bit 2 = 1 sector ID not found
bit 1 = 1 write protect detected during write
bit 0 = 1 ID address mark not found

status register 2 (ST2)
bit 7 = 0
bit 6 = 1 deleted Data Address Mark detected
bit 5 = 1 CRC error in data
bit 4 = 1 wrong cylinder detected
bit 3 = 1 scan command equal condition satisfied
bit 2 = 1 scan command failed, sector not found
bit 1 = 1 bad cylinder, ID not found
bit 0 = 1 missing Data Address Mark

status register 3 (ST3)
bit 7 fault status signal
bit 6 write protect status
bit 5 ready status
bit 4 track zero status
bit 3 two sided status signal
bit 2 side select (head select)
bit 1-0 unit select (0=A 1=B .. )

03F5 w diskette command register. The commands summarized here are
mostly multibyte commands. This is for brief recognition only.

MFM = MFM mode selected, opposite to MF mode.
HDS = head select
DS = drive select
MT = multi track operation
SK = skip deleted data address mark

Command # bytes D7 6 5 4 3 2 1 0
read track 9 0 MFM 0 0 0 0 1 0
0 0 0 0 0 HDS DS1 DS0
specify 3 0 0 0 O O O 1 1
sense drive status 2 0 0 0 0 0 1 0 0
0 0 0 0 0 HDS DS1 DS0
write data 9 MT MFM 0 0 0 1 0 1
0 0 0 0 0 HDS DS1 DS0
read data 9 MT MFM SK 0 0 1 1 0
0 0 0 0 0 HDS DS1 DS0
recalibrate 2 0 0 0 0 0 1 1 1
0 0 0 0 0 0 DS1 DS0
sense interrupt status 1 0 0 0 0 1 0 0 0
write deleted data 9 MT MFM 0 0 1 0 0 1
0 0 0 0 0 HDS DS1 DS0
read ID 2 0 MFM 0 0 1 0 1 0
0 0 0 0 0 HDS DS1 DS0
read deleted data 9 MT MFM SK 0 1 1 0 0
0 0 0 0 0 HDS DS1 DS0
format track 10 0 MFM 0 0 1 1 0 1
0 0 0 0 0 HDS DS1 DS0
dumpreg ** 1 0 0 0 0 1 1 1 0
seek 3 0 0 0 0 1 1 1 1
0 0 0 0 0 HDS DS1 DS0
version ** 1 0 0 0 1 0 0 0 0
scan equal * 9 MT MFM SK 1 0 0 0 1
0 0 0 0 0 HDS DS1 DS0
perpendicular mode ** 2 0 0 0 1 0 0 1 0
0 0 0 0 0 0 WGATE GAP
configure ** 4 0 0 0 1 0 0 1 1
0 0 0 0 0 0 0 0
verify 9 MT MFM SK 1 0 1 1 0
EC 0 0 0 0 HDS DS1 DS0
scan low or equal * 9 MT MFM SK 1 1 0 0 1
0 0 0 0 0 HDS DS1 DS0
scan high or equal * 9 MT MFM SK 1 1 1 0 1
0 0 0 0 0 HDS DS1 DS0
relative seek ** 3 1 DIR 0 0 1 1 1 1
0 0 0 0 0 HDS DS1 DS0

BEWARE: not every invalid command is treated as invalid!
* Note: the scan commands aren't mentioned for the 82077AA.
** Note: EHD controller commands.

03F6 reserved on FDC

03F6 r/w FIXED disk controller data register
bit 7-4 reserved
bit 3 = 0 reduce write current
1 head select 3 enable
bit 2 = 1 disk reset enable
0 disk reset disable
bit 1 = 0 disk initialization enable
1 disk initialization disable
bit 0 reserved

03F7 r/w harddisk controller
bit 6 FIXED DISK write gate
bit 5 FIXED DISK head select 3 / reduced write current
bit 4 FIXED DISK head select 2
bit 3 FIXED DISK head select 1
bit 2 FIXED DISK head select 0
bit 1 FIXED DISK drive 1 select
bit 0 FIXED DISK drive 0 select

03F7 r diskette controller DIR (Digital Input Register, PC/AT mode)
bit 7 = 1 diskette change
bit 6-0 tri-state on FDC

03F7 r diskette controller DIR (Digital Input Register, PS/2 mode)
bit 7 = 1 diskette change
bit 6-3 = 1
bit 2 datarate select1
bit 1 datarate select0
bit 0 = 0 high density select (500Kb/s, 1Mb/s)

conflicts with bit 0 FIXED DISK drive 0 select

03F7 r diskette controller DIR (Digital Input Register, PS/2 model 30)
bit 7 = 0 diskette change
bit 6-4 = 0
bit 3 -DMA gate (value from DOR register)
bit 2 NOPREC (value from CCR register)
bit 1 datarate select1
bit 0 datarate select0

conflicts with bit 0 FIXED DISK drive 0 select

03F7 w configuration control register (PC/AT, PS/2)
bit 7-2 reserved, tri-state
bit 1-0 = 00 500 Kb/S mode (MFM)
= 01 300 Kb/S mode (MFM)
= 10 250 Kb/S mode (MFM)
= 11 1 Mb/S mode (MFM) (on 82072/82077AA)

conflicts with bit 0 FIXED DISK drive 0 select

03F7 w configuration control register (PS/2 model 30)
bit 7-3 reserved, tri-state
bit 2 NOPREC (has no function. set to 0 by hardreset)
bit 1-0 = 00 500 Kb/S mode (MFM)
= 01 300 Kb/S mode (MFM)
= 10 250 Kb/S mode (MFM)
= 11 1 Mb/S mode (MFM) (on 82072/82077AA)

conflicts with bit 0 FIXED DISK drive 0 select

-------------------------------------------------------------------------------
03F8-03FF ---- serial port (8250,8251,16450,16550,16550A,etc.)
same as 02E8,02F8 and 03E8

03F8 w serial port, transmitter holding register, which contains the
character to be sent. Bit 0 is sent first.
bit 7-0 data bits when DLAB=0 (Divisor Latch Access Bit)
r receiver buffer register, which contains the received character
Bit 0 is received first
bit 7-0 data bits when DLAB=0 (Divisor Latch Access Bit)
r/w divisor latch low byte when DLAB=1

03F9 r/w divisor latch high byte when DLAB=1
r/w interrupt enable register when DLAB=0
bits 7-4 reserved
bit 3 = 1 modem-status interrupt enable
bit 2 = 1 receiver-line-status interrupt enable
bit 1 = 1 transmitter-holding-register empty interrupt enable
bit 0 = 1 received-data-available interrupt enable
(also 16550(A) timeout interrupt)

- 16550(A) will interrupt with a timeout if data exists in the
FIFO and isn't read within the time it takes to receive four
bytes or if no data is received within the time it takes to
receive four bytes

03FA r interrupt identification register. Information about a pending
interrupt is stored here. When the ID register is addressed,
the highest priority interrupt is held, and no other interrupts
are acknowledged until the CPU services that interrupt.
bit 7-6 = 00 reserved on 8250, 8251, 16450
= 01 if FIFO queues enabled (16550 only)
= 11 if FIFO queues are enabled (16550A only)
bit 5-4 = 0 reserved
bit 3 = 0 reserved 8250, 16450
= 1 16550 timeout int. pending
bit 2-1 identify pending interrupt with the highest priority
= 11 receiver line status interrupt. priority=highest
= 10 received data available register interrupt. pr.=second
= 01 transmitter holding register empty interrupt. pr.=third
= 00 modem status interrupt. priority=fourth
bit 0 = 0 interrupt pending. contents of register can be used
as a pointer to the appropriate int.service routine
1 no interrupt pending

- interrupt pending flag uses reverse logic, 0=pending, 1=none
- interrupt will occur if any of the line status bits are set
- THRE bit is set when THRE register is emptied into the TSR


03FA w 16650 FCR (FIFO Control Register)
bit 7-6 = received data available interrupt trigger level
00 1 byte
01 4 bytes
10 8 bytes
11 14 bytes
bit 5-4 = 00 reserved
bit 3 = 1 change RXRDY TXRDY pins from mode 0 to mode 1
bit 2 = 1 clear XMIT FIFO
bit 1 = 1 clear RCVR FIFO
bit 0 = 1 enable clear XMIT and RCVR FIFO queues

- bit 0 must be set in order to write to other FCR bits
- bit 1 when set the RCVR FIFO is cleared and this bit is reset
the receiver shift register is not cleared
- bit 2 when set the XMIT FIFO is cleared and this bit is reset
the transmit shift register is not cleared
- due to a hardware bug, 16550 FIFOs don't work correctly (this
was fixed in the 16550A)

03FB r/w line control register
bit 7 = 1 divisor latch access bit (DLAB)
0 receiver buffer, transmitter holding, or interrupt
enable register access
bit 6 = 1 set break enable. serial ouput is forced to spacing
state and remains there.
bit 5 = stick parity
bit 4 = 1 even parity select
bit 3 = parity enable
1 even number of ones are sent and checked in the
data word bits and parity bit
0 odd number of ones are sent and checked
bit 2 = 0 one stop bit
1 zero stop bit
bit 1-0 00 word length is 5 bits
01 word length is 6 bits
10 word length is 7 bits
11 word length is 8 bits

03FC r/w modem control register
bit 7-5 = 0 reserved
bit 4 = 1 loopback mode for diagnostic testing of serial port
output of transmitter shift register is looped back
to receiver shift register input. In this mode
transmitted data is received immediately so that
the CPU can verify the transmit data/receive data
serial port paths.
bit 3 = 1 auxiliary user-designated output 2
bit 2 = 1 auxiliary user-designated output 1
bit 1 = 1 force request-to-send active
bit 0 = 1 force data-terminal-ready active

03FD r line status register
bit 7 = 0 reserved
bit 6 = 1 transmitter shift and holding registers empty
bit 5 = 1 transmitter holding register empty. Controller is
ready toaccept a new character to send.
bit 4 = 1 break interrupt. the received data input is held in
in the zero bit state longer than the time of start
bit + data bits + parity bit + stop bits.
bit 3 = 1 framing error. the stop bit that follows the last
parity or data bit is a zero bit.
bit 2 = 1 parity error. Character has wrong parity
bit 1 = 1 overrun error. a character was sent to the receiver
buffer before the previous character in the buffer
could be read. This destroys the previous
character.
bit 0 = 1 data ready. a complete incoming character has been
received and sent to the receiver buffer register.

03FE r modem status register
bit 7 = 1 data carrier detect
bit 6 = 1 ring indicator
bit 5 = 1 data set ready
bit 4 = 1 clear to send
bit 3 = 1 delta data carrier detect
bit 2 = 1 trailing edge ring indicator
bit 1 = 1 delta data set ready
bit 0 = 1 delta clear to send

- bits 0-3 are reset when the CPU reads the MSR
- bit 4 is the Modem Control Register RTS during loopback test
- bit 5 is the Modem Control Register DTR during loopback test
- bit 6 is the Modem Control Register OUT1 during loopback test
- bit 7 is the Modem Control Register OUT2 during loopback test

03FF r/w scratch register

-------------------------------------------------------------------------------

Adresses above 03FF apply to EISA machines only !

1000-1FFF slot 1 EISA
2000-2FFF slot 2 EISA
3000-3FFF slot 3 EISA
4000-4FFF slot 4 EISA
5000-5FFF slot 5 EISA
6000-6FFF slot 6 EISA
7000-7FFF slot 7 EISA

-------------------------------------------------------------------------------
0401-04D6 ---- used by EISA systems only

0401 r/w DMA channel 0 word count byte 2 (high)
0403 r/w DMA channel 1 word count byte 2 (high)
0405 r/w DMA channel 2 word count byte 2 (high)
0407 r/w DMA channel 3 word count byte 2 (high)

040A w extended DMA chaining mode register, channels 0-3
bit 7-5 reserved
bit 4 = 0 generates IRQ13
= 1 generates terminal count
bit 3 = 0 do not start chaining
= 1 programming complete
bit 2 = 0 disable buffer chaining mode (default)
= 1 enable buffer chaining mode
bit 1-0 DMA channel select

040A r channel interrupt (IRQ13) status register
bit 7-5 interrupt on channels 7-5
bit 4 reserved
bit 3-0 interrupt on channels 3-0

040B w DMA extended mode register for channels 3-0.
bit settings same as 04D6
bit 7 = 0 enable stop register
bit 6 = 0 terminal count is an output for this channel
(default)
bit 5-4 DMA cycle timing
= 00 ISA-compatible (default)
= 01 type A timing mode
= 10 type B timing mode
= 11 burst DMA mode
bit 3-2 Address mode
= 00 8-bit I/O, count by bytes (default)
= 01 16-bit I/O, count by words, address shifted
= 10 32-bit I/O, count by bytes
= 11 16-bit I/O, count by bytes
bit 1-0 DMA channel select

-------------------------------------------------------------------------------
0461 r/w Extended NMI status/control register
bit 7 = 1 NMI pending from fail-safe timer (read only)
bit 6 = 1 NMI pending from bus timeout NMI status (read
only)
bit 5 = 1 NMI pending (read only)
bit 4 reserved
bit 3 = 1 bus timeout NMI enable (read/write)
bit 2 = 1 fail-safe NMI enable (read/write)
bit 1 = 1 NMI I/O port enable (read/write)
bit 0 RSTDRV. bus reset (read/write)
= 0 NORMAL bus reset operation
= 1 reset bus asserted

0462 w Software NMI register. writing to this register causes an NMI
if NMI's are enabled
bit 7 = 1 generates an NMI

0464 r bus master status latch register (slots 1-8). identifies the
last bus master that had control of the bus
bit 7 = 0 slot 8 had control last
bit 6 = 0 slot 7 had control last
bit 5 = 0 slot 6 had control last
bit 4 = 0 slot 5 had control last
bit 3 = 0 slot 4 had control last
bit 2 = 0 slot 3 had control last
bit 1 = 0 slot 2 had control last
bit 0 = 0 slot 1 had control last

0465 r bus master status latch register (slots 9-16)
bit 7 = 0 slot 16 had control last
bit 6 = 0 slot 15 had control last
bit 5 = 0 slot 14 had control last
bit 4 = 0 slot 13 had control last
bit 3 = 0 slot 12 had control last
bit 2 = 0 slot 11 had control last
bit 1 = 0 slot 10 had control last
bit 0 = 0 slot 9 had control last

-------------------------------------------------------------------------------
0481-048B ---- EISA DMA page registers

0481 r/w DMA channel 2 address byte 3 (high)
0482 r/w DMA channel 3 address byte 3 (high)
0483 r/w DMA channel 1 address byte 3 (high)
0487 r/w DMA channel 0 address byte 3 (high)
0489 r/w DMA channel 6 address byte 3 (high)
048A r/w DMA channel 7 address byte 3 (high)
048B r/w DMA channel 5 address byte 3 (high)

-------------------------------------------------------------------------------
04C6-04CF ---- EISA DMA count registers

04C6 r/w DMA channel 5 word count byte 2 (high)
04CA r/w DMA channel 6 word count byte 2 (high)
04CE r/w DMA channel 7 word count byte 2 (high)

-------------------------------------------------------------------------------
04D0-04D1 ---- EISA IRQ control

04D0 w IRQ 0-7 interrupt edge/level registers
bit 7 = 1 IRQ 7 is level sensitive
bit 6 = 1 IRQ 6 is level sensitive
bit 5 = 1 IRQ 5 is level sensitive
bit 4 = 1 IRQ 4 is level sensitive
bit 3 = 1 IRQ 3 is level sensitive
bit 2-0 reserved

04D1 w IRQ 8-15 interrupt edge/level registers
bit 7 = 1 IRQ 15 is level sensitive
bit 6 = 1 IRQ 14 is level sensitive
bit 5 = 1 reserved
bit 4 = 1 IRQ 12 is level sensitive
bit 3 = 1 IRQ 11 is level sensitive
bit 2 = 1 IRQ 10 is level sensitive
bit 1 = 1 IRQ 9 is level sensitive
bit 0 reserved

-------------------------------------------------------------------------------
04D4-04D6 ---- EISA DMA control

04D4 r DMA chaining status

04D4 w extended DMA chaining mode register, channels 4-7
bit 7-5 = 0 reserved
bit 4 = 0 generates IRQ 13
= 1 generates terminal count
bit 3 = 0 do not start chaining
= 1 programming complete
bit 2 = 0 disable buffer chaining mode (default)
= 1 enable buffer chaining mode
bit 1-0 DMA channel select

04D6 w DMA extended mode register for channels 4-7
bit settings same as 04B
bit 7 = 0 enable stop register
bit 6 = 0 terminal count is an output for this channel
(default)
bit 5-4 DMA cycle timing
= 00 ISA-compatible (default)
= 01 type A timing mode
= 10 type B timing mode
= 11 burst DMA mode
bit 3-2 Address mode
= 00 8-bit I/O, count by bytes (default)
= 01 16-bit I/O, count by words, address shifted
= 10 32-bit I/O, count by bytes
= 11 16-bit I/O, count by bytes
bit 1-0 DMA channel select

-------------------------------------------------------------------------------
04E0-04FF ---- EISA DMA stop registers

04E0-04E2 r/w channel 0
04E4-04E6 r/w channel 1
04E8-04EA r/w channel 2
04EC-04EE r/w channel 3
04F4-04F6 r/w channel 5
04F8-04FA r/w channel 6
04FC-04FE r/w channel 7

-------------------------------------------------------------------------------
0530-0533 ---- Gravis Ultra Sound Daughter Card by Advanced Gravis
The I/O address range is dipswitch selectable from:
0530-0533
0604-0607
0E80-0E83
0F40-0F43

0530 r/w Address Select
0531 r/w Data
0532 r/w Status
0533 r/w PIO

-------------------------------------------------------------------------------
0601 w System control. Laptop chipset: Headland HL21 & Acer M5105
bit 7 = 1 power led on
bit 6 = 1 LCD backlight off
bit 5
bit 4
bit 3
bit 2 = 1 video chips disabled, screen blanked.
bit 1
bit 0 = 1 will lock up your machine!

r bit 7 = 0 if screen enabled always these values
bit 6 = 0
bit 5 = 0
bit 4 = 0
bit 3 = 0
bit 2 = 1 (=0 at low power)
bit 1 = 0 power OK
bit 0 = 0

-------------------------------------------------------------------------------
0620-0627 ---- PC network (adapter 1)
0628-062F ---- PC network (adapter 2)

-------------------------------------------------------------------------------
0680 ---- Microchannel POST Diagnostic (write only)

-------------------------------------------------------------------------------
06E2-06E3 ---- data aquisition (adapter 1)

-------------------------------------------------------------------------------
06E8 ---- S3 86C928 video controller (ELSA Winner 1000)

-------------------------------------------------------------------------------
06E8-06EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

06E8 w horizontal displayed

See also 02E8-02EF, 0AE8, 96E8, 9AE8

-------------------------------------------------------------------------------
0746 ---- Gravis Ultra Sound by Advanced Gravis

0746 r Board Version (rev 3.7+)
FF Pre 3.6 boards, ICS mixer NOT present
05 Rev 3.7 with ICS Mixer. Some R/L: flip problems.
06-09 Revision 3.7 and above. ICS Mixer present
0A- UltraMax. CS4231 present, no ICS mixer
w Mixer Control Port

SeeAlso: 0240-024F, 0340-034F

-------------------------------------------------------------------------------
0790-0793 ---- cluster (adapter 1)

-------------------------------------------------------------------------------
0800-08FF ---- I/O port access registers for extended CMOS RAM or SRAM
(256 bytes at a time)
Sometimes plain text can be seen here.

-------------------------------------------------------------------------------
0800-08FF ---- reserved for EISA system motherboard

-------------------------------------------------------------------------------
0A20-0A23 ---- Token Ring (adapter 1)
0A24-0A27 ---- Token Ring (adapter 2)

-------------------------------------------------------------------------------
0AE2-0AE3 ---- cluster (adapter 2)

-------------------------------------------------------------------------------
0AE8 ---- S3 86C928 video controller (ELSA Winner 1000)

-------------------------------------------------------------------------------
0AE8-0AEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

0AE8 w horizontal sync start

-------------------------------------------------------------------------------
0B90-0B93 ---- cluster (adapter 2)

-------------------------------------------------------------------------------
0C00 r/w page register to write to SRAM or I/O

-------------------------------------------------------------------------------
0C00-0CFF ---- reserved for EISA system motherboard

-------------------------------------------------------------------------------
0C7C bit 7-4 (Compaq)

-------------------------------------------------------------------------------
0C80-0C83 ---- EISA system board ID registers

-------------------------------------------------------------------------------
0CF8 ---- Intel Pentium motherboard ("Neptune" chipset)

-------------------------------------------------------------------------------
0CFA ---- Intel Pentium motherboard ("Neptune" chipset)

-------------------------------------------------------------------------------
0EE8 ---- S3 86C928 video controller (ELSA Winner 1000)

-------------------------------------------------------------------------------
0EE8-0EEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

0EE8 w horizontal sync width

-------------------------------------------------------------------------------
1000-10FF ---- available for EISA slot 1

-------------------------------------------------------------------------------
12E8-12EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

12E8 w vertical total

-------------------------------------------------------------------------------
1390-1393 ---- cluster (adapter 3)

-------------------------------------------------------------------------------
1400-14FF ---- available for EISA slot 1

-------------------------------------------------------------------------------
16E8-16EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

16E8 w vertical displayed

-------------------------------------------------------------------------------
1800-18FF ---- available for EISA slot 1

-------------------------------------------------------------------------------
1AE8-1AEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

1AE8 w vertical sync start

-------------------------------------------------------------------------------
1C00-1CFF ---- available for EISA slot 1

-------------------------------------------------------------------------------
1C80-1C8F ---- VESA XGA Video in EISA slot 1

1C80-1C83 r/w EISA Video ID
1C84 r/w EISA Video expansion board control
1C85 r/w EISA Setup control
1C88 r/w EISA Video Programmable Option Select 0
1C89-1C8F r/w EISA Video Programmable Option Select 1-7

-------------------------------------------------------------------------------
1C80-1C83 EISA board product ID (board in slot 1)

-------------------------------------------------------------------------------
1C85 Compaq Qvision EISA - Virtual Controller ID

-------------------------------------------------------------------------------
1EE8-1EEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

1EE8 w vertical sync width

-------------------------------------------------------------------------------
2000-20FF ---- available for EISA slot 2

-------------------------------------------------------------------------------
2100-210F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (first installed)
2110-211F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (second installed)
2120-212F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (third installed)
2130-213F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (fourth installed)
2140-214F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (fifth installed)
2150-215F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (sixth installed)
2160-216F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (seventh installed)
2170-217F ---- IBM XGA (eXtended Graphics Adapter 8514/A) (eighth installed)

-------------------------------------------------------------------------------
2100 ---- XGA Video Operating Mode Register

Note: this port is for the first XGA in the system; 2110-2170 are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2101 ---- XGA VIdeo Aperture Control

Note: this port is for the first XGA in the system; 2111-2171 are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2102-2103 ---- XGA ???

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2104 ---- XGA Video Interrupt Enable

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2105 ---- XGA Video Interrupt Status

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2106 ---- XGA Video Virtual Memory Control

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2107 ---- XGA Video Virtual Memory Interrupt Status

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2108 ---- XGA Video Aperture Index

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2109 ---- XGA Video Memory Access Mode

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
210A ---- XGA Video Index for Data

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
210B ---- XGA Video Data (byte)

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
210C-210F ---- XGA Video Data (word/dword)

Note: this port is for the first XGA in the system; 211x-217x are used for
the second through eighth XGAs

-------------------------------------------------------------------------------
2110-217F ---- secondary XGA adapters (see individual entries above)

-------------------------------------------------------------------------------
22E8-22EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

22E8 w display control

-------------------------------------------------------------------------------
2390-2393 ---- cluster (adapter 4)

-------------------------------------------------------------------------------
23C0-23CF ---- Compaq QVision - BitBLT engine

-------------------------------------------------------------------------------
2400-24FF ---- available for EISA slot 2

-------------------------------------------------------------------------------
27C6 r/w LCD timeout in minutes (Compaq LTE Lite)

-------------------------------------------------------------------------------
2800-28FF ---- available for EISA slot 2

-------------------------------------------------------------------------------
28E9 ---- 8514/A - WD Escape Functions

-------------------------------------------------------------------------------
2C80-2C8F ---- VESA XGA Video in EISA slot 2 (see 1C80-1C8F)

-------------------------------------------------------------------------------
2C80-2C83 EISA board product ID (board in slot 2)

-------------------------------------------------------------------------------
3000-30FF ---- available for EISA slot 3

-------------------------------------------------------------------------------
3220-3227 ---- serial port 3, description same as 03F8
3228-322F ---- serial port 4, description same as 03F8

-------------------------------------------------------------------------------
33C0-33CF ---- Compaq QVision - BitBLT engine

-------------------------------------------------------------------------------
3400-34FF ---- available for EISA slot 3

-------------------------------------------------------------------------------
3540-354F ---- IBM SCSI (Small Computer System Interface) adapter
3550-355F ---- IBM SCSI (Small Computer System Interface) adapter
3560-356F ---- IBM SCSI (Small Computer System Interface) adapter
3570-357F ---- IBM SCSI (Small Computer System Interface) adapter

-------------------------------------------------------------------------------
3800-38FF ---- available for EISA slot 3

-------------------------------------------------------------------------------
3C00-3CFF ---- available for EISA slot 3

-------------------------------------------------------------------------------
3C80-3C8F ---- VESA XGA Video in EISA slot 3

3C80-3C83 r/w EISA Video ID
3C84 r/w EISA Video expansion board control
3C85 r/w EISA Setup control
3C88 r/w EISA Video Programmable Option Select 0
3C89-3C8F r/w EISA Video Programmable Option Select 1-7

SeeAlso: 1C80-1C8F,2C80-2C8F,7C80-7C8F

-------------------------------------------------------------------------------
3C80-3C83 EISA board product ID (board in slot 3)

-------------------------------------------------------------------------------
4000-40FF ---- available for EISA slot 4

-------------------------------------------------------------------------------
4220-4227 ---- serial port, description same as 03F8
4228-422F ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
42E0-42EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

42E1 r/w GPIB (adapter 2)

-------------------------------------------------------------------------------
42E8 ---- 8514/A and hardware-compatible video cards

42E8 r Subsystem Status
42E8 w Subsystem Control

-------------------------------------------------------------------------------
4400-44FF ---- available for EISA slot 4

-------------------------------------------------------------------------------
46E8 ---- VGA video adapter enable

46E8 r/w enable flags
bits 7-5 unused or vendor-specific
bit 4: setup for POS registers (MCA)
bit 3: enable video I/O ports and video buffer
bits 2-0 unused or vendor-specific

Note: IBM uses this port for adapter-card VGAs only, and port 03C3 for
motherboard VGA only

SeeAlso: 03C3

-------------------------------------------------------------------------------
46E8 ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

46E8 w ROM page select

-------------------------------------------------------------------------------
4800-48FF ---- available for EISA slot 4

-------------------------------------------------------------------------------
4AE8-4AEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

4AE8 w Advanced function control
(02h = VGA mode, 03h = 480-line mode, 07h = 768-line mode)

-------------------------------------------------------------------------------
4C00-4CFF ---- available for EISA slot 4

-------------------------------------------------------------------------------
4C80-4C83 EISA board product ID (board in slot 4)

-------------------------------------------------------------------------------
4C80-4C8F ---- VESA XGA Video in EISA slot 4 (see 3C80-3C8F)

SeeAlso: 1C80-1C8F,6C80-6C8F

-------------------------------------------------------------------------------
5000-50FF ---- available for EISA slot 5

-------------------------------------------------------------------------------
5220-5227 ---- serial port, description same as 03F8
5228-522F ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
5400-54FF ---- available for EISA slot 5

-------------------------------------------------------------------------------
5800-58FF ---- available for EISA slot 5

-------------------------------------------------------------------------------
5C00-5CFF ---- available for EISA slot 5

-------------------------------------------------------------------------------
5C80-5C8F ---- VESA XGA Video in EISA slot 5

5C80-5C83 r/w EISA Video ID
5C84 r/w EISA Video expansion board control
5C85 r/w EISA Setup control
5C88 r/w EISA Video Programmable Option Select 0
5C89-5C8F r/w EISA Video Programmable Option Select 1-7

SeeAlso: 2C80-2C8F,4C80-4C8F,6C80-6C8F

-------------------------------------------------------------------------------
5C80-5C83 EISA board product ID (board in slot 5)

-------------------------------------------------------------------------------
6000-60FF ---- available for EISA slot 6

-------------------------------------------------------------------------------
62E0-62EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

62E1 r/w GPIB (adapter 3)

-------------------------------------------------------------------------------
63C0-63CF ---- Compaq QVision - BitBLT engine

-------------------------------------------------------------------------------
6400-64FF ---- available for EISA slot 6

-------------------------------------------------------------------------------
6800-68FF ---- available for EISA slot 6

-------------------------------------------------------------------------------
6C00-6CFF ---- available for EISA slot 6

-------------------------------------------------------------------------------
6C80-6C83 EISA board product ID (board in slot 6)

-------------------------------------------------------------------------------
6C80-6C8F ---- VESA XGA Video in EISA slot 1

6C80-6C83 r/w EISA Video ID
6C84 r/w EISA Video expansion board control
6C85 r/w EISA Setup control
6C88 r/w EISA Video Programmable Option Select 0
6C89-1C8F r/w EISA Video Programmable Option Select 1-7

SeeAlso: 1C80-1C8F,2C80-2C8F,5C80-5C8F

-------------------------------------------------------------------------------
7000-70FF ---- available for EISA slot 7

-------------------------------------------------------------------------------
7400-74FF ---- available for EISA slot 7

-------------------------------------------------------------------------------
7800-78FF ---- available for EISA slot 7

-------------------------------------------------------------------------------
7C00-7CFF ---- available for EISA slot 7

-------------------------------------------------------------------------------
7C80-7C83 EISA board product ID (board in slot 7)

-------------------------------------------------------------------------------
7C80-7C8F ---- VESA XGA Video in EISA slot 7

7C80-7C83 r/w EISA Video ID
7C84 r/w EISA Video expansion board control
7C85 r/w EISA Setup control
7C88 r/w EISA Video Programmable Option Select 0
7C89-7C8F r/w EISA Video Programmable Option Select 1-7

SeeAlso: 1C80-1C8F, 6C80-6C8F

-------------------------------------------------------------------------------
8000-80FF ---- available for EISA slot 8

-------------------------------------------------------------------------------
82E0-82EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

82E1 r/w GPIB (adapter 4)

-------------------------------------------------------------------------------
82E8-82EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

82E8 w current Y position

-------------------------------------------------------------------------------
82F8-82FF ---- serial port, description same as 03F8
83F8-83FF ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
83C0-83CF ---- Compaq QVision - Line Draw Engine

-------------------------------------------------------------------------------
83C4 ---- Compaq Qvision EISA - Virtual Controller Select

-------------------------------------------------------------------------------
83C6-83C9 ---- Compaq Qvision EISA - DAC color registers

-------------------------------------------------------------------------------
8400-84FF ---- available for EISA slot 8

-------------------------------------------------------------------------------
86E8-86EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

86E8 w current X position

-------------------------------------------------------------------------------
8800-88FF ---- available for EISA slot 8

-------------------------------------------------------------------------------
8AE8-8AEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

8AE8 w destination Y position / axial step constant

-------------------------------------------------------------------------------
8C00-8CFF ---- available for EISA slot 8

-------------------------------------------------------------------------------
8C80-8C83 EISA board product ID (board in slot 8)

-------------------------------------------------------------------------------
8EE8-8EEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

8EE8 w destination X position / axial step constant

-------------------------------------------------------------------------------
9000-90FF ---- available for EISA slot 9

-------------------------------------------------------------------------------
92E8-92EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

92E8 w error term

-------------------------------------------------------------------------------
9400-94FF ---- available for EISA slot 9

-------------------------------------------------------------------------------
96E8-96EF ---- 8514/A and hardware-compatible video cards

96E8 r Enter WD Enhanced Mode
96E8 w major axis pixel count

-------------------------------------------------------------------------------
9800-98FF ---- available for EISA slot 9

-------------------------------------------------------------------------------
9AE8h-9AE9h ---- 8514/A Graphics Processor Status

9AE8w r bit 9: hardware busy
9AE8 w command

-------------------------------------------------------------------------------
9C00-9CFF ---- available for EISA slot 9

-------------------------------------------------------------------------------
9C80-9C83 EISA board product ID (board in slot 9)

-------------------------------------------------------------------------------
A220 ???? soundblaster support in AMI Hi-Flex BIOS ????

-------------------------------------------------------------------------------
A2E0-A2EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

A2E1 r/w GPIB (adapter 5)

-------------------------------------------------------------------------------
A2E8-A2EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

A2E8 w background color

-------------------------------------------------------------------------------
A6E8-A6EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

A6E8 w foreground color

-------------------------------------------------------------------------------
AAE8-AAEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

AAE8 w write mask

-------------------------------------------------------------------------------
AEE8-AEEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

AEE8 w read mask

-------------------------------------------------------------------------------
AFFF r/w plane 0-3 system latch (video register)

-------------------------------------------------------------------------------
B220-B227 ---- serial port, description same as 03F8
B228-B22F ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
B2E8-B2EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

B2E8 w color compare

-------------------------------------------------------------------------------
B6E8-B6EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

B6E8 w background mix

-------------------------------------------------------------------------------
BAE8-BAEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

BAE8 w foreground mix

-------------------------------------------------------------------------------
BEE8-BEEF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

BEE8 w multi-function control

-------------------------------------------------------------------------------
C008 ---- Intel Pentium motherboard ("Neptune" chipset)

-------------------------------------------------------------------------------
C050 ---- Intel Pentium motherboard ("Neptune" chipset)

C050 r/w bit 2: ???

-------------------------------------------------------------------------------
C052 ---- Intel Pentium motherboard ("Neptune" chipset)

C052 r/??? bits 6,7: ???

-------------------------------------------------------------------------------
C220-C227 ---- serial port, description same as 03F8
C228-C22F ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
C2E0-C2EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

C2E1 r/w GPIB (adapter 6)

-------------------------------------------------------------------------------
D220-D227 ---- serial port, description same as 03F8
D228-D22F ---- serial port, description same as 03F8

-------------------------------------------------------------------------------
E2E0-E2EF ---- GPIB (General Purpose Interface Bus, IEEE 488 interface)

E2E1 r/w GPIB (adapter 7)

-------------------------------------------------------------------------------
E2E8-E2EF ---- 8514/A and compatible video cards (e.g. ATI Graphics Ultra)

E2E8 w pixel data transfer

-------------------------------------------------------------------------------

MEMORY-MAPPED ADDRESSES

-------------------------------------------------------------------------------
80C00000 Compaq Deskpro 386 system memory board register

80C00000 w RAM relocation register
bit 7-2 Reserved, always write 1's.
bit 1 = 0 Write-protect 128-Kbyte RAM at FE0000.
= 1 Do not write-protect RAM at FE0000.
bit 0 = 0 Relocate 128-Kbyte block at FE0000 to address 0E0000
= 1 128-Kbyte RAM is addressed only at FE0000.

80C00000 r Diagnostics register
bit 7 = 0 memory expansion board is installed
bit 6 = 0 second 1 MB of system memory board is installed
bit 5-4 = 00 base memory set to 640 KB
01 invalid
10 base memory set to 512 KB
11 base memory set to 256 KB
bit 3 = 0 parity error in byte 3
bit 2 = 0 parity error in byte 2
bit 1 = 0 parity error in byte 1
bit 0 = 0 parity error in byte 0 (in 32-bit double word)

-------------------------------------------------------------------------------
C0000000-C000FFFF Weitek "Abacus" math coprocessor

-------------------------------------------------------------------------------




-------------CREDITS-------------------------
Chuck Proctor <71534.2302@CompuServe.COM>
Richard W. Watson <73042.1420@CompuServe.COM>

[Some of the information in this list was extracted from Frank van Gilluwe's
_The_Undocumented_PC_, a must-have book for anyone programming down to the
"bare metal" of a PC.]

[Some of the information in this list from the shareware version of Dave
Williams' DOSREF, v3.0]

[8514/A hardware ports found in FractInt v18.0 source file FR8514A.ASM]

[Compaq QVision info from the _COMPAQ_QVision_Graphics_System_Technical_
_Reference_Guide_, second edition (October 1993). Compaq part number
073A/0693. Much more to come!]
</nowiki></pre>

Latest revision as of 15:18, 2 October 2020

An I/O port is usually used as a technical term for a specific address on the x86's IO bus. This bus provides communication with devices in a fixed order and size, and was used as an alternative to memory access. On many other architectures, there is no predefined bus for such communication and all communication with hardware is done via memory-mapped IO. This also increasingly happens on modern x86 hardware.


Looking for a list of ports

As an operating system developer, you should not be looking for this. "Standardized" I/O ports are only used in some situations, such as hardware that was present on pre-PCI (AT and compatible, etc.) PC hardware. Examples of devices using "standardized" I/O ports are the floppy drive, serial and parallel ports, However, most ports are claimed by plugin cards[which?] you might not have and some[which?] are even assigned via PNP which means that any port could be used for the device in question. If you want access to a device, you will need to look up the details for the device in question, and if some fixed port is involved, it will tell you. It is not technically feasible to have a complete mapping of ports to devices as you won't get access to it.

Port abuse

A few devices[which?] were made cheap and do not decode all address bits of the I/O port in question (only the bottom 12 or 14). That means that there are up to sixteen port addresses mapping to the same device. Similarly, some devices have chosen to avoid conflict with such devices by using a sparse register file. The bottom bits would be defined as constant, and the top bits would instead be used for the index. You would get ports number 0x82E8, 0x84E8, 0x86E8 and so on. Such ISA devices are typically prone to interfering with PCI assigned IO addresses due to their spread.

Modern implementations of old devices (typically IDE and VGA controllers) have an implementation that is mentioned to be plug-and-play with moving registers, but they are still able to listen to legacy ports and respond accordingly.

The list

If you have found a port number and you are still wondering what it's meant to do, here's a list of the most common ports:

Port range Summary
0x0000-0x001F The first legacy DMA controller, often used for transfers to floppies.
0x0020-0x0021 The first Programmable Interrupt Controller
0x0022-0x0023 Access to the Model-Specific Registers of Cyrix processors.
0x0040-0x0047 The PIT (Programmable Interval Timer)
0x0060-0x0064 The "8042" PS/2 Controller or its predecessors, dealing with keyboards and mice.
0x0070-0x0071 The CMOS and RTC registers
0x0080-0x008F The DMA (Page registers)
0x0092 The location of the fast A20 gate register
0x00A0-0x00A1 The second PIC
0x00C0-0x00DF The second DMA controller, often used for soundblasters
0x00E9 Home of the Port E9 Hack. Used on some emulators to directly send text to the hosts' console.
0x0170-0x0177 The secondary ATA harddisk controller.
0x01F0-0x01F7 The primary ATA harddisk controller.
0x0278-0x027A Parallel port
0x02F8-0x02FF Second serial port
0x03B0-0x03DF The range used for the IBM VGA, its direct predecessors, as well as any modern video card in legacy mode.
0x03F0-0x03F7 Floppy disk controller
0x03F8-0x03FF First serial port

See Also

External Links

Retrieved from "https://osdev.wiki/wiki/I/O_Ports?oldid=17950"