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I have an old Thinkpad X32 which has an Intel(R) Pentium(R) M processor 1.80GHz based on the result of cat /proc/cpuinfo and I was wondering which is better to use on it, the i386 or the i686 version of the Fedora ISO found here.

Basically, I don't know how to determine if my CPU is an i386 or an i686. If you could also tell me how I can get this data, please let me know.

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up vote 5 down vote accepted

Basically, i686 is for Pentium Pro/II and later, while i386 covers 386 and 486 CPUs as well. From http://forums.fedoraforum.org/showthread.php?t=198771:

i want to know that what is the meaning and difference between i386 and i686 specified at the end of each package..?

Compiled for different CPU architectures. i386 should run fine on anything above a 386 processor. i686 is for newer Pentium processors (by new I mean PII and above), but can also be run on newer Intel Core 2 Duos, Athlons, etc.

So i686 should work; pretty much anything newer than the Pentium Pro or Pentium II is i686.

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Thanks. Just curious, will i386 run better, or as efficiently, on an i686 machine? – Eric Jun 18 '12 at 23:19
Isn't a Pentium 1 a i586? – CodesInChaos Jun 19 '12 at 7:06
@CodeInChaos indeed. fixing my answer – Renan Jun 19 '12 at 11:54
@Eric if a binary is compiled for i686 a good compiler should use features that make certain steps faster than in the i386-architecture. So i386 should be slower on a Pentium. – Nils Jun 19 '12 at 20:55

Look up i686: it means P6, and

The first implementation of the P6 core was the Pentium Pro CPU in 1995, the immediate successor to the original Pentium design (P5).

Unless your computer is an embedded device running an older i386 processor (there are a few of these, not many), or is more than 15 years old, pick i686.

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