Re: scaling beyond 4 processors

The perhaps odd thing is that just about any alternative to quad-Xeon
is likely to be _way_ better.  There are some context switching
problems that lead to it being remarkably poorer than you'd expect.
Throw in less-than ideal performance of the PAE memory addressing
system and it seems oddly crippled overall.

We've been getting pretty good results with IBM pSeries systems;
they're expensive, but definitely very fast.

Preliminary results with Opterons are also looking very promising.
One process seemed about 25x as fast on a 4-way 8GB Opteron as it was
on a 4-way 8GB Xeon, albeit with enough differences to make the
comparison dangerous.
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