Author: Robert Hyatt
Date: 20:15:03 12/04/02
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On December 04, 2002 at 20:29:52, Bob Durrett wrote: > >The recent threads shed some light on the issue of when one is more important >than another, but the answer is sketchy and seems to be "depends." > >For current chess-playing programs, which is more important? Latency or >bandwidth? Why? > >Is the answer different if multiple processors are used? > >Bob D. First, chess engines have a bad habit of doing real random-access probes to memory for things like hashing. That is latency-dependent rather than bandwidth because we are not reading large chunks, but small scattered 16-32 byte blocks... That said, programs do need some bandwidth as you have to keep the cpu fed with instructions and data and that stuff resides in memory unless the program is small enough to tuck away in L1/L2/L3 cache. multiple processors increases the bandwidth requirement. Two cpus require twice the bandwidth as one, and generally, high-end server boards provide two- way memory interleaving to double the bandwidth. Given the choice of 2x the bandwidth or 1/2 the latency, I'd go for reducing the latency. But that is basically impossible. Latency as been stuck at 100-120ns for 20+ years now...
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