• Yokemate of Keyboards
    Yokemate of Keyboards
    Posts: 12025 from 2003/5/22
    From: Germany
    > I don't know, Andreas. From that statement, I would gather that all
    > floating point operations are performed by one hardware unit designed
    > the execute all three of sets of instructions.

    Read further: "The VSU is the combination of the Altivec execution unit and the 4 FPUs." I read it as the VSU consisting of smaller (sub-)units like for instance the AltiVec unit. But maybe I'm just reading it wrong and it means that the VSU is now what "the Altivec execution unit and the 4 FPUs" had been before, i.e. in former implementations like POWER4/5/6 or PPC970.

    > Therefore, VSX isn't a superset of the VMX/Altivec instructions

    Yes, that's what I concluded, regardless of VSX and AltiVec being two distinctive physical units or being both executed by just one single unit.

    > While a new PPC processor might be designed to only support VSX,
    > it seems unlikely that IBM would want to do that.

    Yes, but it's not only IBM I'm looking at. See (last sentence):


    > I don't know what you define as a superset


    > but if Altivec is equivalent to Intel MMX , then VSX can be
    > see as an analog of the later SSE instruction sets.

    That sounds reasonable.
  • »10.08.10 - 22:45