IBM 610 workstation computer 3465

+--------------- Only up to a hundred thousand processors, or so. ;-) Seriously, PowerPC (Power4-5 etc.) does 8-way SMP as a basic building block. Intel x86 is at least 4-way and AMD Opterons up to 8-way without bridges, though NUMA not SMP. Opteron's NUMA is coherent, though. +---------------

Opterons are ccNUMA (cache-coherent NUMA, the "cc" is important!), with all of the main memory visible to all of the CPUs, which *is* "SMP" as far as user programs can tell except that a cache-line miss will taken less time if the main memory it's fetching from is "here" rather than "over there". Though Opteron's simulation of a snoopy bus by using broadcast messages starts to slow things down above 4 CPUs or so but can be sped up again by hardware buttist like the "Horus" chip from Newisis..

SGI's Origin & Altix are also ccNUMA, but use a different hardware cache-coherency protocol ("directory-based"), and because of that they scale up to *hundreds* of CPUs max of 512 CPUs per Linux image on the Altix 3700 with *terabytes*(!) of main RAM visible to all of

Again, the only difference a user program sees between a "true SMP" and a "ccNUMA" system is that there's more variance in the cache-line miss delays on the ccNUMA system at the same number of CPUs, and that ccNUMA systems can scale up to *far* more CPUs than anyone has even gotten "true SMP" to ever work.

This is not particularly new stuff; SGI was shipping 64- to 256-CPU Origin systems in the late 1990's.

-Rob

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