[RC5] Re: A whole bunch of things

Ryan Dumperth woodie at indy.net
Fri Nov 21 16:57:54 EST 1997


>there is no advantage on a PPC's to work in float.  Alpha's might get an
>advantage since they're optimized for float.

The reason the PPC was mentioned is that it is a third faster at floating
point math than Intel's offerings, which are in turn significantly faster
than their clones. A PPC 604e/200 gets an 8.9 on SPECfp95 compared to a
P6/200's 6.7. Both PPCs and x86's have only one floating point pipeline.
The most important "optimization" in Alphas, Ultras, R10000, and even the
IBM POWER series is that they all have two FP pipes. I have a feeling that
the PPC 604e's biggest advantage over the P6 in FP calculations is that
PPCs can issue four instructions per clock, compared to the P6's three,
which happens to coincide exactly with the PPC's speed advantage.

Not that any of that has the slightest bearing on RC5, although it will
matter more when we have multiple projects available.

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