• Yokemate of Keyboards
    Yokemate of Keyboards
    Andreas_Wolf
    Posts: 10977 from 2003/5/22
    From: Germany
    > I stumbled at something weird: The dnetc client "Benchmark all" reports values significantly
    > lower for iMac G5 than for a G4 PowerBook 1,67 GHz. Here are the results [in nodes/sec]: [...]

    Per-clock performance normalized to "1.00 = slowest" is this:

    OGR-NG | RC5-72

    1.04 | 1.06 : PowerMac G5 Quad

    1.01 | 1.04 : PowerMac G5 Dual Processor
    1.00 | 1.00 : iMac G5

    1.35 | 1.47 : PowerBook G4

    As can be seen, your iMac G5 results scale quite well with your PowerMac G5 results, so if the iMac results are weird, the PowerMac results must be weird too.

    > What could be the cause?

    Usually, the per-clock AltiVec performance is significantly lower with the G5 compared to the G4. If you look at the G4 and G5 results of the individual benchmark tests OGR-NG and RC5-72 are composed of, you should be able to see this behaviour with the AltiVec-supporting benchmark tests.

    Edit: Looking at my 2016 dnetc results (G4, G5) for the individual scalar (non-SIMD) RC5-72 tests, it can be seen that the G4 is 15...87% faster per clock than the G5 even with those scalar tests (usually G5 is faster per clock than G4 for dedicated scalar code). It seems that the old hand-crafted PPC assembly code of dnetc was never adapted to the peculiarities of the PPC970 microarchitecture, so that a 60x/7xx microarchitecture is assumed for the scalar tests and a 74xx microarchitecture is assumed for the AltiVec-enabled tests.

    [ Edited by Andreas_Wolf 21.05.2020 - 12:18 ]
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