Date: Wed, 7 Jul 1999 22:10:08 +0200
To: pgcc AT delorie DOT com
Subject: Re: K7 potentials
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In-Reply-To: <3.0.32.19990707152354.010ceec0@pop.xs4all.nl>; from Vincent Diepeveen on Wed, Jul 07, 1999 at 03:23:55PM +0100
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From: Marc Lehmann <pcg AT goof DOT com>
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On Wed, Jul 07, 1999 at 03:23:55PM +0100, Vincent Diepeveen wrote:
> I'm also looking forward to a motherboard that supports 4 or 8 K7s.
> Considering its expected selling prize, and the fact that we finally
> get competition for the Xeon now, this really will be a big step forward!

I believe this will be just as expensive as their intel counterparts. And
worse, such an OpenPIC board would be a totally new design, with totally
new implementation errors ;) But my opinion doesn't really count anything
here ;)

> For the program crafty (crafty is in some official benchmarks by
> the way, so it makes sense to test it; the command 'bench'
> gives you after a few minutes a benchmark in crafty; ftp ftp.cis.uab.edu

However, you need to modify crafty a bit to get deterministic results
(crafty varies moves).

> for crafty. linux versions of crafty are compiled using pgcc)

But only with -O, as this gives the best results with long longs (sadly).

> See specs Merced, note that merced has quite some
> registers; work to do for the compilerfreaks! 

I never get tired of announcing the EPIC page at
http://www.goof.com/pcg/epic/, which offers quite a bit information on
that subject.

> When compiling my program for some RISC processors i get the impression
> registers don't get used very smartly (gcc for the alpha

gcc is especially bad at using registers, yes. Especially bad on x86,
but still not perfect on other architectures. There is big room for
improvements.

> So i guess compilers not using the major part of the merced registers
> will be commercial suicide!

There are quite a bit larger problems with the merced than just using
registers. You need a totally different model, and heavy data as well as
control speculation.

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