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Date: Tue, 09 Sep 2008 13:48:51 -0400
From: Mark Lord <lkml@....ca>
To: Andi Kleen <andi@...stfloor.org>
Cc: Krzysztof Halasa <khc@...waw.pl>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
Arjan van de Ven <arjan@...radead.org>,
x86 maintainers <x86@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] x86 fixes
Mark Lord wrote:
> Andi Kleen wrote:
>> Krzysztof Halasa <khc@...waw.pl> writes:
>>
>>> Linus Torvalds <torvalds@...ux-foundation.org> writes:
>>>
>>>> - "modern 32-bit": PPro and better. Can take CMOV, MMX and TSC for
>>>> granted.
>>> VIA C3 (Samuel 2/Ezra, 600 - 1000 MHz?, common on VIA EPIA-*: home
>>> theatres etc) can't CMOV.
>>
>> AFAIK they fixed that in newer BIOS with a microcode update. It's
>> slow, but it works.
> ..
>
> Our firewall here uses a Via C3-600 CPU, and CMOV has never worked on it.
> But based upon your posting, I have today upgraded the BIOS to the
> latest (2004) version.
>
> Now.. how can I check whether CMOV works or not? It's not listed in
> /proc/cpuinfo.
..
H. Peter Anvin wrote:
>
> Compile just about any C program with -march=i686.
..
Okay, done. And the binary does indeed have a ton of CMOV instructions.
When running it, this appears immediately:
Illegal instruction
So much for the "BIOS upgrade fixes CMOV microcode" theory.
Cheers
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