IA32 Architecture Family

The following tables and notes constitute an overview of the x86-based processors produced (most of which are still available in some form today). These tables are intended as a guide only, the most reliable way to determine CPU features (amongst newer CPUs at least) is by using CPUID.

The table is fairly easy to read, but a note on some of the values would be helpful. Values marked with Yes are available in all CPUs in that series, no exceptions. Items marked with No are not available at all. Items marked with Maybe are available in some of the CPUs (maybe higher speced machines, for instance the 486DX, or in later processor steppings). Items marked with a ? are yet to be researched or confirmed. If you have some information, let us know!

Most of the information in this table comes from Wikipedia, with some coming from the Intel and AMD processor manuals.

Intel Processors

These processors from Intel use the CPUID string "GenuineIntel".

	Release Date	FPU (80x87)	SMP	MMX	PAE	SSE	Hyper-threading	EM64T/AMD64	Notes
8086	1978	Optional	No	No	No	No	No	No, 16-bit only	First processor of the long-lasting x86 ISA, only supporting 16-bit real mode and 64KB segmentation. Eight 16-bit general-purpose registers, four 16-bit segment registers, a 16-bit instruction pointer, and a 16-bit flags register. 256 interrupts available and a 64KB I/O space.
80186	1982	Optional	No	No	No	No	No	No, 16-bit only	Designed and intended for embedded systems. First x86 processor with ENTER/LEAVE instructions, as well as PUSHA/POPA, a few other instructions, and immediate modes for PUSH, IMUL, and shift instructions. Exception 06h (Invalid Opcode, #UD) introduced with the UD2 "instruction".
80286	1982	Optional	No	No	No	No	No	No, 16-bit only	First x86 processor with a "protected mode" and a 24-bit address bus and can not go from pmode to real mode without a CPU reset. It has better performance in real mode than the previous 16-bit Intel processors. Designed for multitasking and multi-user systems.
80386	1985	Optional	No	No	No	No	No	No	Successor to the 80286, the Intel 386 is the first processor of the IA32 architecture. It has 32 bit wide registers, supports 4 kByte paging, and a flat memory model in addition to the segmented memory model of the 80286.
80486	1989	Optional	No	No	No	No	No	No	The 486 integrates a 80x87 FPU on-chip (not the 486SX though), and supports power saving functions (System Management Mode, Stop Clock, Auto Halt Powerdown).
Pentium	1993	Yes	Yes	No	No	No	No	No	The Pentium integrates an APIC (which may be permanently disabled by the BIOS). It also supports 2-way multiprocessing.
Pentium Pro	1995	Yes	Yes	No	Yes	No	No	No	The Pentium Pro supports PSE (36 bit physical address space with 4 MiB pages) and PAE (36 bit physical address space with 2 MiB and/or 4 KiB pages), but does not have the MMX registers of the Pentium.
Pentium MMX	1996	Yes	Yes	Yes	No	No	No	No	The Pentium MMX is very similar to the original Pentium CPU, but includes MMX SIMD registers (single instruction, multiple data). It doesn't seem logical, but the Pentium MMX was released after the Pentium Pro.
Pentium II	1997	Yes	Yes	Yes	Yes	No	No	No	The Pentium II again supports MMX (as well as PAE), as well as additional low-power states: AutoHALT, Stop-Grant, Sleep, and ~DeepSleep.
Pentium II Xeon	1998	Yes	Yes	Yes	Yes	No	No	No	The Xeon supports 4/8/+ way multiprocessing.
Pentium III	1999	Yes	Yes	Yes	Yes	SSE	No	No	Available in speeds from 450MHz to 1400MHz, the Pentium III was the first to support SSE (128 bit packed single FP SIMD). Other than this it was widely similar to the Pentium II Deschutes.
Pentium III Xeon	1999	Yes	Yes	Yes	Yes	SSE	No	No
Pentium IV	2000	Yes	Yes	Yes	Yes	SSE2/(3)	Yes	Maybe
Pentium M	2003	Yes	Yes	Yes	Yes	SSE2	No	No
Core	2003	Yes	Yes	Yes	Yes	SSE3	No	No
Xeon 51xx	2006	Yes	Yes	Yes	Yes	SSSE3	Yes	Yes
Core 2	2006	Yes	Yes	Yes	Yes	SSE4.1	No	Yes
Xeon 54xx	2007	Yes	Yes	Yes	Yes	SSE4.1	No	Yes
Core i7	2008	Yes	Yes	Yes	Yes	SSE4.2	Yes	Yes
Atom 200/300	2008	Yes	Yes	Yes	Yes	SSSE3	Yes	Yes
Atom N-series	2008	Yes	Yes	Yes	Yes	SSSE3	Yes	No
Atom Z-series	2008	Yes	Yes	Yes	Yes	SSSE3	Yes	No

Advanced Micro Device Intel-compatible Processors

The biggest competitor to Intel at this time (2004 August). They came into being slightly after Cyrix with a 5k86 (being a 486 compatible similar to the 5x86, don't confuse them) and then followed it up by a K6 processor. This one was faster than the Pentiums, and more popular than the Cyrix ones because they both didn't rate it (afaik), and they didn't overheat (as was claimed, untrue, for the Cyrixes).

The CPUID identifier string is "~AuthenticAMD"

It is important to note that the "SSE" used by AMD and the "SSE" used by Intel are actually not compatible, not fully at least (somebody verify this?). This causes lots of confusion.

	Release Date	FPU (80x87)	SMP	MMX	3DNow!	PAE	SSE	Hyper-threading	EM64T/AMD64	Notes
K5	1996	Yes	No	No	No	?	No	No	No	AMD's first try at a Pentium-compatible CPU. Not a huge success, mostly due to low clock speeds.
K6	1997	Yes	No	Yes	No	?	No	No	No	Actually designed by NexGen (who AMD took over), the K6 is a fully Pentium-compatible CPU. It outperformed the Pentium in several areas. One notable instruction was the LOOPcc instruction, which execuced in 2 cycles compared to a Pentium's 18, causing problems.
K6-2	1998	Yes	No	Yes	Yes	?	?	No	No	AMD had a lesson learned there, don't make your processor too fast in some instructions. Not that they were put off by that, they just added 16 wait states to the execution of the LOOPcc and thus caused it to slow to the speed of a Pentium. AMD didn't just do this however. They added a special case (speculation, might be coincidence) for the DEC (E)CX; Jcc combination, which is semantically equivalent with the LOOPcc instruction, but this semantic equivalence and the loop being faster on Intels caused the loop instruction to always be used. Nobody used the DEC/Jcc combo. They kept the original speed for this combo and specified in their optimization manuals that this was the preferred method over the loopcc instruction. It also featured a new technology, the 3DNOW! technology, which was MMX using floating point numbers, and multiplexed (again) on the floating point registers. The K6-2 was quite popular, and scaled higher than the P1 ever did. It was largely compatible with the P2, but (afaik) not completely.
K6-3	1999	Yes	?	Yes	Yes	?	?	No	No	They started this design off with the concept of not making it underpowered in any place, and to make it at least P2 compatible. It was fully P2 compatible. The K6-3 was not too popular, mainly because the K6-2 did very well and people didn't see why they should buy a more expensive K6-3 for the same amount of megahertz. This of course was a joke, same as it is to call a 2GHZ opteron slower than a 2.2GHZ celeron. A little known fact about the K6-3 is that it is in fact an Athlon, minus a few instructions, and minus one very important piece. The K6-3 suffered from a bottleneck at the instruction decode unit (which converts the X86 instructions to native instructions). It could only handle 2 in a cycle, which it made during about 20-30% of the cycles for average software. For optimized software you could bring it to 100% easily, and still want another channel. This wasn't too weird, because it did have 3 execution units of each type (ALU / MMX / loadstore) which were not used much at all. Note that these units are units executing the native instructions, so making 3 of each is not a stupid idea. They needed a new front end, and of course a new copy of instructions from Intel.
Athlon	?	Yes, not x87?	?	Yes	Yes	?	?	?	No

Athlon (first try)

The first models of the Athlon were distinct, they were the first time that a competitor to Intel actually had a faster processor, without Intel having a backup plan. It was poised against the PIII, which at that time was their top model and best-running one too. The athlon beat them to the 1GHZ mark, and at that time the 1GHZ had become completely irrelevant. It just meant that they had a new size to mark their processors with. Intel missed the point here, and they did until very shortly ago. The GHZ myth had been broken, the Athlon at 1.1GHZ was still faster than the PIII at 1.3GHZ, and people knew. They didn't go for a P3 if a faster athlon was available at a lower clock speed, and at a lower price.

Athlon XP / MP / Duron (new style)

AMD switched to a big offensive, trying to persuade the buyers to demand AMD CPU's instead of being OK with Intels. The new versions of these processors were all just a tad better than the previous one, could do a slight number of instructions more (the Athlons started with not even SSE1, and from model 6 (both Athlon and Duron) they supported it). The processors also advanced very slightly in each other direction, making each new type just a tad faster than the previous one. In the end of the GHZ wars (past year, about) the fastest Athlon was running at 2.2GHZ, but outperformed the better half of the 3GHZ P4's.

AMD64 based CPU's

This is slightly offtopic here, but still quite relevant, since these processors all support the entire IA32 family natively. AMD created a new processor, with 64-bit (actually 48-bit, but who notices those 16 bits?) memory addressing and 64-bit calculations, being very compatible with the old style CPU's. So compatible, that the core for 32-bit and 64-bit is essentially equal, aside from the size of calculations and the support of a few encodings that were in effect redundant. They removed a few 1-byte opcodes (about 20 in total, including all 1-byte INC and 1-byte DEC instructions) to make place for a new REX prefix. They modified it to use 16 registers instead of 8, added a load of new names, got the old software working, and optimized the 32-bit performance to unprecedented levels. These CPU's outperform the P4 at any clock speed, in almost (1/20 programs not) any calculation-intensive program. This made them very popular, but also very expensive, The cheapest nowadays is around 180 dollars, or euro's.

Other CPU vendors making similar chips

Cyrix

Cyrix was a well-known CPU vendor from the 386 years (and slightly before) up to the Pentium II times, when it more or less vanished inside Via. Via now uses the name as a CPU name (not making it clearer), but this section is about the Cyrix CPU's. The processors supporting CPUID call it a "CyrixInstead"

Cyrix 387

This isn't actually a processor, but is the most famous Cyrix processor. It was the fastest coprocessor to the 386 to be found, and was even very usable aside a 486-SX. These were the main line of money for Cyrix.

Cyrix 4x86

A processor that had the abilities of a 486. The first generation plugged into 386 sockets giving greater speeds without requiring extra hardware updates. Later editions could also be used on 486 motherboards.

Cyrix 5x86

A processor that performed as a 486 and was socket-compatible. It features some of the pentium's abilities, but not all (such as cmpxchg8b).

Cyrix 6x86 / M1

This processor is, even though the name suggests otherwise, compatible with the 586 (Pentium). It didn't contain any of the MMX or PPro features but is nevertheless very nice. It performed slightly better per cycle compared to the Pentium Pro, and was thus given ratings. This was the time they were loathed for rating their processors, since the performance of floating point operations was lower than that of the Pentium Pro

Cyrix 6x86MX / M2

Was a Pentium MMX compatible processor, also using ratings which gave it a bad name to start with. It was again socket-compatible to the Pentium MMX and the older Pentiums (without MMX). It supported a few features from the Pentium Pro, among which the very usable CMOVcc set. This however wasn't well known at the time, and nobody seemed to care.

MediaGX

This was a chip that apart from the CPU, included several peripherals on-chip including graphics and audio devices.

The company was bought by National Semiconductor, who sold the trademark to VIA. The MediaGX was developed further and was eventually bought by AMD who marketed it as the Geode.

Rise Technologies

I've only heard about this company making Pentium-compatible chips, without MMX, but I don't know any detail but the CPUID identifier string. It just stuck. The string was "RiseRiseRise", or the same in all 3 dwords (making a search for it very easy).

See Also

Threads

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