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Introducing the PowerPC SIMD unit

Posted by Hemos on from the one-name-to-rule-them dept.

An anonymous reader writes "AltiVec? Velocity Engine? VMX? If you've only been casually following PowerPC development, you might be confused by the various guises of this vector processing SIMD technology. This article covers the basics on what AltiVec is, what it does -- and how it stacks up against its competition."

3 of 83 comments (clear)

  1. tradeoffs by idlake · · Score: 1, Flamebait

    Choosing something like AltiVec involves a bunch of trade-offs:

    -- How much work do I need to do in order to take advantage of it? Some BLAS implementations may support it and some Fortran 95 compilers may generate code for it for some primitives, but other than that, it's a lot of manual work to tune code for it. (My own experience with using the AltiVec instructions can only be described as "painful", among other things because the C interface to them is poorly defined and causes name conflicts.)

    -- What range of hardware can I choose from? Well, there is mainly one Apple rack-mount that runs OS X, a bunch of big Apple desktops in fancy cases, and a bunch of expensive IBM workstations. That's pretty limited.

    -- What's the bang for the buck? There are actually two parts to this: what's the bang for the buck for code not specifically hacked to take advantage of AltiVec, and what's the bang for the buck for code specifically hacked for AltiVec. For code not specifically tuned for AltiVec, the bang for the buck is not so great with either Apple or IBM. For the rest, it may be reasonable.

    Considering these issues, I continue to find AltiVec pretty unpersuasive. I think AltiVec won't take off until Intel and AMD's SIMD instructions are equally good; until then, there is simply not enough incentive for software writers to incorporate support into their software for it consistently. And then, frankly, we first need a market in commodity Linux PowerPC boxes until that really gets interesting. I wouldn't hold my breath.

  2. Re:Does it matter? by leereyno · · Score: 0, Flamebait

    If I wanted a slow laptop, I'd at least buy one that comes with a screen and a keyboard.

    Lee

    --
    Muslim community leaders warn of backlash from tomorrow morning's terrorist attack.
  3. What it means... by turgid · · Score: 0, Flamebait
    ...is that this is yet another IBM PR fluff piece liberally sprinkled with FUD and half-truths.

    We get on average one of these per month posted here to slashdot as news.

    Nothing to see here. Move along please.

    --
    Stick Men