Author: Gian-Carlo Pascutto
Date: 11:27:24 09/03/03
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On September 03, 2003 at 14:17:56, Robert Hyatt wrote: >You are hung up on the X86 SMP platform. Forget X86. Just think "SMP". > >Go look at the Cray XMP/YMP/C90/T90. They use a crossbar. _not_ a bus. >A good C90 for example has 16 processors, 4096 banks of memory, all with a >big crossbar connecting them. any processor can access any bank in 120ns, >unless two bang on the same bank. Then there is a 10ns penalty or so >added in (bank busy delay). > >The point is that SMP does _not_ mean "shared bus" except for the world of >the PC and some other smaller SMP boxes (Sun, alpha, etc.) "you give me two boxes that are identical except for SMP vs NUMA, the SMP box will _always_ have a speed advantage." To Cray or not to Cray, I have seen no proof of the above, on the contrary. I gave a counterexample, which you've not refuted. -- GCP
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