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Subject: Re: P4?

Author: Gerd Isenberg

Date: 10:23:40 10/16/03

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<snip>
>Being off by a factor of 2-3 is not very significant when dealing with numbers
>posted by Vincent.  :)  a number within a factor of 2-3 for him is an
>_excellent_ approximation.

Hehe, you and Vincent are really incorporated in doing side blows ;-)

AMD64's 16 128-bit register became the default floating point register in
64-bit windows - during context switch x87-stack (MMX) is not saved/restored.
What i found curious about SSE2 is that the xxm-registers have i kind of type
state (int,float,double) and different instruction sets for load/store,
arithmetic of course, but even for bitwise and/or/xor (to reset/set/toggle sign
bit in floats?). The instructions use the same execution units. "False" type
instructions result in some penalty cycles.

> However, that notwithstanding, the C90 can certainly
>produce 6 floating point results every 4 nanoseconds, as a theoretical peak.

A vector of 128*128-bit each, may be including memory access?

>  It
>can sustain 4 (about 1 GFLOPS) with many codes, and go beyond that for certain
>special cases.  It is hard to imaging a PC coming anywhere near that, even
>comparing today's PC with the C90 which is 13 years old.  There are much faster
>Cray's around today...

Maybe the performance timegap between super computer and PC becomes closer.
Is there any trend?




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