Author: Robert Hyatt
Date: 08:42:03 08/26/03
Go up one level in this thread
On August 26, 2003 at 03:00:52, Johan de Koning wrote: >On August 25, 2003 at 18:04:29, Robert Hyatt wrote: > >>A single cpu that will run crafty at 1M nps has a cache-cache and cache-memory >>bandwidth of X bytes/second. A single cpu that runs crafty at 2M nps has >>exactly twice the cache-cache and cache-memory bandwidth and twice the clock >>frequency. A dual-cpu just needs two cpus, but the two cpus give twice the >>cache-cache bandwidth, but _no_ improvement in cache-memory bandwidth. > >Nope, C2M bandwith is constant, regardless of n and f (hence constant :-). Actually it isn't. Some duals use interleaving. Some don't. All quads I have here use 4-way interleaving to ramp up the bandwidth significantly. All machines are _not_ created equal... > >Furtunataly C2M is not part of the equation. Unless n * f gets large AND all n >processes make a habit of trashing their own cache or their fellow processors >caches. But that just doesn't happen. > >>This was all about memory bandwidth with respect to copy/make. > >Nope, this was about memory having nothing to do with it. > >... Johan And there we disagree. Otherwise copy/make would be a big win for me too. It wasn't...
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