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"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> > I was discussing this with a friend of mine last night, and his theory was that
> > the G5 is using SIMD, which the Phenom II doesn't seem to have.  I suppose that
> > -could- make a difference with number crunching...
> >
> The 1090T supports SSE1-SSE3 SIMD extensions, according to cpu-world, however I
> can't tell if it actually uses SIMD technology.
>
> According to Everymac, the 970MP G5 processor uses SIMD and supports up to 12
> simultaneous out-of-order instructions.  If it is, indeed, doing four
> calculations per instruction, that might account for the difference.
>
> looking at the Makefile for my AMD install, the -march option is set to "native"
> which resulted in the build being optimized for X86_64-unknown-linux-gnu,
> whereas the G5 install is optimized specifically for powerpc64-unkonwn-linux-gnu
> | PowerPC G5.
>
> Regards,
> A.D.B.

Povray only uses SIMD registers and instructions as scalar entities (so on x86
processors, SSE2 is faster than x87).

The SIMD unit in the 970 is single precision only, so Povray will not use it.
Povray uses double precision floats. So on the 970, the regular FP unit is used.

Try this on both computers:

1) copy the benchmark.pov file to your home directory.
2) run the following command:
../povray +ibenchmark -w512 -h512 +a0.3 +v -d +f -x

This makes sure of the render size. Then compare the output images produced by
both computers.

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