Author: Robert Hyatt
Date: 21:02:50 03/23/02
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On March 23, 2002 at 16:09:55, Tom Kerrigan wrote: >On March 23, 2002 at 13:38:45, Dan Andersson wrote: > >>SMT is of little or no consequence to chess programs. It might even slow it >>down. You don't think it automatically doubles the amount of functional units on >>a given CPU, do you? > >You're completely missing the point. SMT was invented and implemented because >most of a chip's functional units are idle at any given point in time--using >them for another thread gives you free performance. > >I haven't seen any benchmarks yet, but a quad P4 Xeon will appear to software as >an 8-way system and while it will probably not be as fast as a full-on 8-way >system, it will be much faster than a 4-thread system. > >-Tom This is only true of _one_ of the two threads can run mainly out of cache. The processor will have the other thread stalled waiting on memory reads or writes. If the second thread needs memory, it is over... But if it can run out of cache, it can fill in the gaps nicely...
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