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CPU Naming Schemes - x86 (386,486,586), AMD 64, IA64 & EM64T Print E-mail

A Brief Explanation of CPU Naming Schemes:


Download Linux:

Supported Architectures: 386, 486, 586, 686, AMD x86-64, Intel IA-64, PowerPC




This purpose of this article is to explain these architectures in brief so that you won’t get confused next time regarding the architecture of your machine.


First of all, Linux and many other operating systems refer to different Intel CPU generations as i386, i486, i586 and i686. Strictly speaking, i386 refers to the 80386 processor family, i486 refers to the 80486 processor family, i586 refers to Intel Pentium or Pentium MMX processors, and i686 refers to all Pentium Pro and later processors.
However, all Intel CPUs are backward compatible with all previous Intel CPUs. Since most operating systems today only deal with 80386 CPUs and later, they therefore often use i386 to refer to the Intel architecture as a whole, since the i386 term includes all Intel CPUs that they can run on.


Since all these processors were based on the same architecture (basically they read/wrote 1's and 0's in the same way), and their names all contained "86", the whole family was collectively called "X86". All the X86 processors including and after the 386 are 32-bit.

Intel stopped at i686 since the Pentium Pro's architecture was so flexible that they didn't need to change it fundamentally after that. To check, from within Linux, which i?86 you have, check the contents of the file /proc/cpuinfo . If it says "cpu family: 6", you have an i686. Similar for 3, 4 and 5.
or running the command:

#uname -m


Frequently, the name IA32 is also used. It stands for "the 32-bit Intel Architecture", and it refers to all 32-bit Intel CPUs, that is to say every 80386 CPU or later. In other words, it is the term that really should be used instead of "i386" to refer to all CPUs that are compatible with the 80386 CPU.


The term x86 does strictly refer to all Intel-compatible processors since the 8086, but it's much more commonly used in the same sense as IA32 or i386, i.e. to refer to all processors compatible with the 80386.

The recent trend has been to move toward 64-bit processors, and several different architectures popped up. DEC's Alpha and Motorola's PPC chips have been 64-bit for a while, but Intel's Itanium and Xeon and AMD's Athlon64 are the new kids on the block.


The difference between the Itanium (IA64) and PowerPC (PPC) versus the Athlon64 is that the Itanium and PPC have completely different architectures (they speak different 1 and 0 languages), whereas the Athlon64 speaks the same language as the 32-bit X86 processors, but adds 64-bit memory registers. Therefore the name of the Athlon64 in generic terms is "X86_64".

The 64-bit architecture that AMD pioneered and Intel followed, i.e. the architecture used in the Athlon64s and Intel's EM64T CPUs, is referred to by many names. The most common ones are AMD64, x86-64, x86_64 or x64.

 Intel, not to be outdone, has since redesigned its 64-bit Xeon processors to use the same kind of architecture as the Athlon64, calling it "Intel Extended Memory 64 Technology" (EM64T).

The Intel Core processors come in two types. The original Core Duo processor is a 32-bit processor with two cores. The Core 2 Duo is a 64-bit processor with two cores. The Core Duo (to the best of my knowledge) is a regular X86 processor, while the Core 2 Duo is an X86_64.

Recently certain models of the Pentium 4 processor (not just the Xeon) are being shipped with "EM64T" technology. These processors (such as the Intel Pentium 4 521) are essentially the same as an AMD64 in their architecture, and are capable of running both 32-bit software and OS’s as well as 64-bit. Software compiled for AMD64 should work on these processors.

 A quick review:


Intel x86-compatible processors, including Intel Pentium and Pentium-MMX, Pentium Pro, Pentium-II, Pentium-III, Celeron, Pentium 4, Xeon, Core Duo, and Centrino/Centrino Duo; VIA C3/C3-m and Eden/Eden-N; and AMD Athlon, AthlonXP, Duron, AthlonMP, Sempron, and Turion


PowerPC processors, such as those found in Apple Power Macintosh, G3, G4, and G5, and IBM pSeries systems


64-bit AMD processors such as Athlon64/FX/X2, Turion64, Opteron; and Intel 64-bit processors such as EM64T

  • Did you know that it was Intel that designed the first microprocessor (i.e. a processor on a single chip) ever? That's right: the 4-bit Intel 4004. Released in late 1971, its maximum clock speed was a staggering 740 kHz.






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