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Subject: Re: Huge Caches Mean Faster Chess Engines?

Author: Robert Hyatt

Date: 08:04:23 06/24/02

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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?

Right idea, yes.  Although "improving it" is non-trivial.  Memory speeds
have not changed very much at all in 20+ years.  It is doubtful they will
unless we get away from capacitive storage (DRAM) technology.  Dumping
charges here and there will _never_ get any faster, due to basic resistance,
capacitance and inductance present in any electrical circuit.





>
>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.

always...



>
>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.


Using cache isn't really a compiler issue.  It is a _programmer_ issue.



>
>If anybody here understands this stuff, please explain everything. :)
>
>Summary:  Bigger caches mean better chess engines?

To a limit.


>
>Bob D.



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