Author: Robert Henry Durrett
Date: 07:27:05 06/24/02
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On June 24, 2002 at 09:48:14, Gian-Carlo Pascutto wrote: >On June 24, 2002 at 08:49:15, Robert Henry Durrett wrote: > >> >> >>Apparently, "memory bandwidth" limitations result in chess computer performance >>limitations. I don't really understand the details, but it's supposed to be >>true. In fact, I don't really understand "memory bandwidth." I assume it is >>some sort of limitation on how fast information can be written to or retrieved >>from RAM. Presumably, new technology would improve this. Do I have this right? >> >>So, the logical solution seems to be to minimize the number of times the program >>has to "go to memory," which I interpret as "going to RAM." It would seem that >>extensive use of caches would help in that regard. >> >>Someone pointed out recently that it takes only a few clock cycles to read or >>write to a cache [depending on which cache] but takes a huge number of clock >>cycles to do that with RAM. >> >>Now they're saying that the new Intel Itanium microprocessors have huge caches. >>[Also huge prices!] >> >>Doesn't this suggest that judicious use of huge caches [in preference to RAM] >>would produce better chess engines? This assumes that there is a way for the >>programmer to actually accomplish this. The right compilers must be used. >> >>If anybody here understands this stuff, please explain everything. :) >> >>Summary: Bigger caches mean better chess engines? > >The programmer doesn't have to do anything to make use of the caches >of the CPU's. The cache is simply a faster kind of memory. If the program >reads something from (slow) RAM, the cache will remember that information. >The next time the program wants to read that value, the cache can return >it and the program does not have to wait for the RAM. This is all handled >by the CPU, i.e. no additional effort for the programmer. > >As far as I know, memory bandwith is _not_ a limiting factor of most >chess-engines, but memory latency is. Caches will help with that as well. This "latency issue" is interesting. Could you please elaborate? How do the caches help? Bob D. > >-- >GCP
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