OSDev.wiki

Virtual 8086 Mode: Difference between revisions

[unchecked revision][unchecked revision]
← Older edit
Content deleted Content added
VisualWikitext
No edit summary
m Bot: Replace deprecated source tag with syntaxhighlight
 
(One intermediate revision by one other user not shown)
Line 2:
 
==Entering V86==
[[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]] {{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}} [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]] {{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}} [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]] {{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}} [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]] {{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}} [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Eiriley.jpg]] [[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]][[File:Dayn.jpg]] {{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}{{BeginnersWarning}}
 
The CPU is executing in virtual 86 mode when the VM bit (bit 17) is set in the ''EFLAGS'' register. If you want to enter virtual 86 mode you must set this bit to 1.
Line 21 ⟶ 20:
EFLAGS.VM is NEVER pushed onto the stack if the V86 task uses PUSHFD. You should check if CR0.PE=1 and then assume it's V86 if that bit is set.
 
<sourcesyntaxhighlight lang="asm">
detect_v86:
smsw ax
and eax,1 ;CR0.PE bit
ret
</syntaxhighlight>
</source>
 
VM mode detection is mainly useful when writing DOS extenders or other programs that could be started either in plain real mode or in virtual mode from a protected mode system. An 'ordinary' bootloader shouldn't worry about this since the BIOS will not set up VM86 to read the bootsector ;)
Retrieved from "https://osdev.wiki/wiki/Virtual_8086_Mode"