Why is 64 bit faster. RE: [Beowulf] Win64 Clusters!!!!!!!!!!!!

Mark Hahn hahn at mcmaster.ca
Mon Apr 16 16:43:24 PDT 2007

> registers.  AMD had to include x87 for 32-bit compatibility,
> but there was no way they were going to beef up its number
> of registers for 64-bit mode when they had the better SSE2
> alternative.

making x87 better could be done fairly easily: just get rid of 
the stack-based register set ;)

> HPC folk that only needed single precision FP could have
> been avoiding x87 on x86 architectures since 1999,
> which isn't that long ago, in my opinion.

are there really so many SP HPC apps?

> However, HPC folk with dual precision FP codes running
> on x86 couldn't avoid x87 until SSE2 was introduced in 2001.
> I was using AMD processors and they didn't get SSE2 support
> until 2003.

and 80-bit (long double) still works pretty well on x87...

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