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Subject: Re: Processor's

Author: Jeremiah Penery

Date: 18:06:51 06/17/04

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On June 15, 2004 at 06:33:57, David Mitchell wrote:

>Crafty is so cache-stingy, it might not make a big difference, but I'd be amazed
>if a program like TSCP, wouldn't see a sizeable difference if the L2 cache size
>was doubled.

TSCP probably fits in any processor's L2 cache, and even the L1 cache of
Athlons.  So increasing L2 cache size won't help it at all.  Crafty should enjoy
at least some benefit from increasing the cache size (up to 1MB, or perhaps
more).

>Of course, I've been amazed before, and nothing beats a little testing - all
>theories aside, you see the darndest results!

The reason that increasing cache size doesn't increase the speed of chess
programs is that almost all the memory accesses in a chess program are hash
probes, which will cause cache miss and must go to main memory, which is very
much slower.
If you make the hash table small enough to fit inside the cache, then maybe you
will see some benefit in terms of NPS from making cache bigger (because you can
increase hash table size and still be in cache), but your time to solution will
go up also with the smaller hash table.



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