Altivec - how much faster is it?

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Anywhere from 1x to 16x performance. It really depends.

More things can be accelerated for AltiVec than other 'SIMD' units since it has a more complete instruction set. Also it has the permute operator which is useful in various non-SIMD operations.

The most important factor is, of course, the ability of the programmer. :-D

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Tigger, that's not correct at all. Ignore whomever gave you this misinformation from now on.

The AIM alliance all have access to the complete PowerPC instruction set. The 162 instructions which AltiVec is comprised of are freely available to all partners. In fact the original engineer who pushed the PowerPC alliance to develop a vector unit was a former Motorola employee working for Apple. There was at no point a restriction made on IBM to produce slow CPUs, that's just 100% rumor bullshit. Motorola doesn't 'own' the instructions, only their implementation which they called AltiVec (which was originally called VMX and after Velocity Engine).

BTW Apple going AMD is another 100% bullshit rumor.

Stop reading rumors, I mean really.

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@minator,

Even with the new PPC 970 quad-pumped bus architecture AltiVec is still starved for data.