[ILUG] Advice on number crunching?

[Matthew French]

Nick Murtagh asked:
> On Thursday 14 March 2002 14:41, Matthew French wrote:
> > On the PPC vs Intel issue, I was also surprised by the results. They
would
> > seem to indicate there is something wrong with the machine architecture
as
> > the PPC chip should do integer and floating point math at least as well
as
> > an equivalent MHz Pentium. I have had experiences in the past where two
>
> Why? They use quite different architectures.

Yes, but integer and floating point math are pretty straightforward
operations. The pentium's deep pipeline should not provide too many
advantages, nor should the extra registers or the RISC functionality of the
PPC. Assuming that most relevant data is in L1 cache,
and that the code has been properly compiled, one should expect the
processors to be handling each instruction optimally. Which would translate
to a roughly equivalent number of instructions cycles per loop. I would
expect the PowerPC to be somewhat faster because it does not have to support
the same legacy instructions as the Pentium does.

Looking at some SPECint results:

An IBM pSeries 610[1] 333MHz turns in results of roughly 226 and 329:

A 500MHz Intel Pentium III[2] gives 231 and 191.

Obviously these are total system benchmarks, and if I searched hard enough I
could most probably find other results to show that the PowerPC is slower
than the Pentium 4. But the difference quoted in the Register seems absurd.
They do allude to the fact that it is a NeXT/BSD integration issue and not
related to the processor but even this should not result in such a big
difference.

Anyway, it looks like there is something wrong with the G4. Hopefully it was
a problem with the test and not a fundamental design flaw.

- Matthew

[1] I think the pSeries is a PPC3 processor?
[2] This results were published using Windows XP, so we should most probably
increase them by 30% to find out how much the processor really can do. :)



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