Author: Bo Persson
Date: 13:35:10 08/26/02
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On August 26, 2002 at 11:07:25, Robert Hyatt wrote: >On August 26, 2002 at 05:13:35, Vincent Lejeune wrote: > >> >>Waiting for the real numbers ... > > >Read that again, carefully. "local memory". This is NUMA. The penalty for >accessing memory that is _not_ local is significant. The penalty for accessing >local memory is still 100ns or so, because nobody knows how to reduce >resistance, capacitance and inductance together. > >When you have multiple processors there will be significant conflicts. I don't >know whether that "hypertransport bus" if full-duplex or not. If it is, it >might work OK for two processors, but not beyond two as there would be no easy >way to manage more than two. Theoretically they could. The more-than-2-way Hammers, the Opteron, have 4 sets of the hypertransport logic. Would work fine for quad boxes. The local memory channel is also separate. They have a *lot* of pins... > I assume it is a "normal bus" which means if >the two processors want to access each other's local memory, one is definitely >going to wait. And that also means there is some sort of bus negotiation >protocol which extends latency as well... Probably! Bo Persson bop2@telia.com
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