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Subject: Re: Xeon and hyperthreading

Author: Eugene Nalimov

Date: 22:05:06 10/18/02

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Actually, you don't need lot of functional units. Even single functional unit
will become unused the moment you need the data that is not in L1 cache.
(Slightly oversimplified, but you got the idea).

I saw reasonable speedup (low tens of percents) on large server application.
Some (de)compression code runs almost exactly 2x faster.

I strongly suspect chess program will benefit much less, mainly due to the extra
nodes parallel version has to search. And in any case OS and application should
be hyperthreading-aware. For example, spinlock loops have to be rewritten.

Thanks,
Eugene

On October 18, 2002 at 22:04:34, Dan Andersson wrote:

>Add to that the fact that hyperthreading will have no positive effect
>whatsoever. It's not like the P4 core has a lot of unused funtional units to
>spare.
>
>MvH Dan Andersson



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