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Subject: Re: Sempron vs. Athlon 64: Proof that Crafty's working set is < 256k

Author: Eugene Nalimov

Date: 14:52:58 08/20/04

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On August 20, 2004 at 04:33:07, Tom Kerrigan wrote:

>Now that AMD is selling two processors that are identical other than L2 cache
>size (Sempron has 256k, Athlon 64 has 512k) we have proof of Crafty's working
>set size:
>
>Sempron:    1,080,020 NPS
>Athlon 64:  1,080,230 NPS
>
>http://www.anandtech.com/linux/showdoc.aspx?i=2170&p=3
>
>This should prove once and for all that Crafty's working set is < 256k and
>therefore that size of L2 cache has no effect on its performance (as long as
>it's >= 256k) and that main memory speed likely plays a trivial role
>performance-wise.
>
>I bring this up because of all of the long debates that have occurred in the
>past about the value of L2 cache, the speed of memory, and the working set size
>of chess programs.

If you remember, several years ago I run the similar experiment. I benchmarked
Crafty on 900MHz Itanium2 with 1.5Mb of L2 cache, and on 900MHz Itanium2 with
3Mb of L2 cache.

I don't remember exact numbers (I posted them here), but the 3Mb cache was
faster by (I believe) 10%.

Unfortunately that did not answer original question, as CPUs have not only
different cache size, but also different cache associativity. 1.5Mb was 6-way
associative. 3Mb was 12-way associative.

Thanks,
Eugene

>I have no doubt that Crafty uses a bunch of memory, but obviously not with
>enough temporal locality for it to matter one iota.
>
>-Tom



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