Author: Jeremiah Penery
Date: 22:16:46 12/04/02
Go up one level in this thread
On December 04, 2002 at 23:15:03, Robert Hyatt wrote: >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... I'm not sure why you persist in giving this 100-120ns number, when several credible sources have said that the figure of today is no more than 75ns.
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