Author: Jeremiah Penery
Date: 15:38:34 08/26/03
Go up one level in this thread
On August 26, 2003 at 11:42:03, Robert Hyatt wrote: >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... A great many single-CPU motherboards you can buy offer dual-channel memory and/or 4-way memory interleaving. I don't know if many of the SMP (2-CPU, specifically) boards for Intel or Athlon have that stuff or not. Opteron doesn't worry about it, as each CPU has its own dedicated (dual-channel) memory, and N CPUs have N times the aggregate bandwidth of a single-CPU machine.
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