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Re: XP1000 and Linux



> That would indicate Greg's view that compilers don't
> effect streams is significantly off. Also worries me
> that this system, with look ahead still is so sensitive
> to compilers. I'd bet the DUNIX cc is capable of unrolling
> loops to give the processor more things to look at as it
> does it's out of order execution... I'll see about hand
> unrolling the loops to see how that changes it's performance.

Unrolling never does much for STREAM in this day and age -- main
memories are very slow compared to processors. Just look at the
numbers for how many cycles it takes to refill a L3 cache line.  It is
a bit surprising that lack of any optimization changes the number so
dramatically. When I get my boxes I'll report Digital cc and egcs
numbers on the same hardware.

BTW, the "standard" 128 megabyte config for the XP1000 leaves half the
dimm slots empty. Oh, and the person who was wondering why a DP264
with 1 processor might make sense: twice as many dimm slots as the
XP1000.

-- g




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