Author: Robert Hyatt
Date: 14:13:47 08/22/02
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On August 22, 2002 at 16:25:10, Yen Art Tham wrote: >On August 22, 2002 at 13:43:06, Robert Hyatt wrote: > >>On August 22, 2002 at 13:38:17, Rajen Gupta wrote: >> >>>in practical terms how much faster would an 8 way processor be for the most >>>scaleable commercial chess programme which i believe is shredder? >>> >>>rajen >> >> >>If it turned out to be 1.5X faster than a 4-way that would probably be >>a huge plus... memory is a problem on 2-way and 8 way boxes... > > >In what way is memory a "problem" on a dual? >Please elaborate. > >yat Memory bandwidth is severely limited on a normal PC. On a dual, you simply add a second processor, which then competes for memory bandwidth with the first processor. As a result, a dual machine is generally not 2x faster than a single. For the quad (4 cpu machines) the manufacturers use a more sophisticated chipset that provides 4x the memory bandwidth by doing 4-way memory interleaving. As a result, on a quad, each CPU sees about the same bandwidth potential as a single-cpu machine sees. On an 8-way box, the chipset still relies on 4-way interleaving, but you have 8 processors. IE it will perform about like 4 dual-cpu machines, which is not quite as good as you would expect from 8 cpus...
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