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Mail Archives: pgcc/2000/01/26/08:42:29

Date: Wed, 26 Jan 2000 11:43:02 +0100 (CET)
From: Martin Ockajak <mandos AT hq DOT alert DOT sk>
To: pgcc AT delorie DOT com
Subject: Re: pgcc on AMD K6
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On Fri, 14 Jan 2000, Robert Varga wrote:

> > Check the Makefile, if there are any refs to -mpentiumpro, (which I did see, though I think that's supposed to only enable the scheduling for Pentium Pro),
> > -march=pentiumpro or -march=i686, change them to -march=k6. Also, don't use i686 ASM, which may also contain Pentium Pro specific opcodes. K6 doesn't support cmove, but
> > AMD Athlon does (I just checked mine, and WCPUID says it does)
> 
> K6-2 tests show that more optimal combination would be
> -march=pentium -mcpu=pentiumpro

yes, it seems that current PPro machine desc. matches K6-2 better
than K6 description
one of the reasons is IMHO unrealistic K6 branch costs model
but there are others too
i wrote some support for K6-2/3 and it seems to be promising
but i'm not satisfied with the performance yet
and of course i have to test it some more
i'll send it then

this brings me the question:
Should the K6-2/3 support be apart from K6 support
(so we would have -mcpu=k62 and -mcpu=k6)
or should it be just generic K6 support (as currently is)
but aimed mostly on K6-2/3 (well, K6 an K6-2/3 are different but
not "very" different)
any suggestions ? 

> don't really know about the K-3.

well, according to K6-3 specs
K6-3 is nothing more than K6-2 plus 256KB L2 cache
which makes difference in overall performance but doesn't make difference
in insns scheduling at all

- ------------------------------------------------------------------------------
Martin Ockajak a.k.a. Mandos  <mandos AT hq DOT alert DOT sk>  http://hq.alert.sk/~mandos
"The goal of Computer Science is to build something that will last at
least until we've finished building it."
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