Re: Claimed 486/Pentium CPU "flaw"

Michael L. Galbraith (mikeg@weiden.de)
Thu, 19 Feb 1998 05:39:45 +0100 (MET)


On Thu, 19 Feb 1998, MOLNAR Ingo wrote:

>
> On Wed, 18 Feb 1998, David C Niemi wrote:
>
> > There is an interesting article about underperformance of pre-Pro x86
> > processors on:
> > http://www.intelligentfirm.com/membench/index.shtml
>
> i suspect this is the same 'cache line access stall' thing observed &
> posted by Robert Collins to comp.sys.intel a few months ago? If you look
> at the Linux pentium FPU-memcpy patch, it's basically already optimized
> for such an access type, although the correct order of memory accesses was
> not found by analyzing the processor's (undocumented) behavior, it was
> found via experimentation (according to the author). This patch has been
> available for more than 2 years now AFAIR ...
>
> -- mingo

I've been running that patch since inception with nothing but nice
(very) performance wins. Any idea why it hasn't been assimilated?

-Mike

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