Re: cpuinfo & Cyrix 6x86

Albert Cahalan (
Thu, 28 Nov 1996 02:35:52 -0500 (EST)

>>> Why is the Cyrix 6x86 seen as a 486 in /proc/cpuinfo?
>>> Isn't it a Pentium-class cpu?
>> It is only a fast 486.
> This is an inaccurate statement.

If the chip was compatible with the Pentium, it would be identified
as such. Obviously, the chip has something incompatible about it.

> Please read the Cyrix 6x86 architecture handbook, available from
> Cyrix's web site in PDF format. Or I can bounce them to you,
> if you prefer.

I'll read it if you send me the URL and it is not too large.

I suspect that you refer to a useless document that describes
the RISC-like internal workings of the CPU. That does not matter.
The CPU could contain little fairies that do math in their heads.

What matters is the features supported. The Cyrix chip does not
support Pentium 4 MB pages. I know the chip has a related feature
that only Linux will ever use, but that is not the same as Pentium
4 MB pages. The Cyrix chip does not support Intel SMP motherboards.
I don't think it has the cycle counter. If is _does_ support all
those things, then at least the CPUID instruction is broken! :-)

The Cyrix chip is a fast and cheap CPU that is compatible with
the i486. Maybe that is not a bad thing, but it is not a Pentium.