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Inside the PowerPC 970
daveschroeder writes "Jon "Hannibal" Stokes has posted a long-awaited, very detailed analysis of the IBM PowerPC 970 at Ars Technica. Notable quote: 'The 970 was made for Apple'."
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Floating point ops, optimized for graphics processing and things like compression (jpeg, mpeg, mp3). If you read the Ars article he waxes on about it's superiority over MMX/SSE/SSE2.
AltiVec is important for Apple marketing because it lets them claim impressive performance figures without actually needing to push the state of the art in terms of processor design further than Intel.
No, AltiVec is important for Apple full stop - in the short term to make up for the anemic bus speeds allowed by the G4, and in the longer term because a SIMD unit is now as expected a component of modern desktop CPUs as an FPU is.
And even something like a hand-coded vectorized BLAS library doesn't help because most scientific software still doesn't use such libraries
The only thing you can really sure about "most" scientific software is that it needs an FPU. Scientists and engineers do a huge variety of simulations, some of which are vectorizable and some of which aren't.
If AltiVec has a weakness in the scientific field, it's the lack of support for double precision. And there's nothing in the instruction set which precludes this, so I wouldn't be surprised to see it appear in some future CPU.
Imagine how much better it would be if Apple could ship systems based on the 970 today, rather than after a few months additional delay due to AltiVec.
If it didn't have AltiVec, it wouldn't be what Apple needs in a desktop CPU - not much point in getting what you don't need a few months early (not like that would happen anyway: this isn't lego: you can't unplug "the AltiVec bits" without any impact on the rest of the design).
And every dollar and watt that is shaved off the AltiVec price makes it a much more viable processor for servers and blades, which would get volume up and prices down.
Except that Apple aren't currently in the blade market at all, and have a fairly small presence in the more general server market. If they can sell a few boxes there, fine, but getting the volume up means targetting consumers - not server farms.
Nae bother