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'."

Comments

In the market for a 64-bit workstation?

[idiotnot]

Fast forward a few months....hmm...a few options:

Sun: Nice hardware, very expensive, CDE.
AMD: Commodity hardware, cheap, WinXP.
HP: Intel hardware, very expensive, CDE or WinXP.
I think I know what I'd buy.

Of course, the Athlon64/Opteron would get quite a bit of consideration due to my hobbies.

But I think it'd end up being the Mac.

Re:In the market for a 64-bit workstation?

[Bold Marauder]

AMD, NetBSD in place of XP? ;)

Dual FPUs!

[Anonymous Coward]

Reading through the article, its nice to see some real design going into a processor. Looking through Intel's last few chips, they've been upping ther clock speed and packing in more cache.

Yeah, yeah, they are hog-tied because you can't easily re-compile the entire windows platform to use new instruction sets. Linux users, of course, don't have this problem (muhahahah).

Did anyone else catch the bit on the twin FPU's? I'm just imagining what this thing is going to do with vector operations and frequency transforms.

For most of you non-engineers:

-Most 3d vector operations are affine tranformations. Using a 4x4 array of floating point numbers you can translate, rotate, and scale. Works beautifully, but it's a lot of calculations.

-The Fast Fourier Transform (FFT) is used a lot in signal processing. It's a floating point monster.

Re:drop AltiVec

[Apotsy]

You'd be surprised how much stuff in Mac OS X is AltiVec optimized. Even memcpy gets a boost from it. It's a lot more than just a "gimmick".

integer FFTs aren't uncommon

[Trepidity]

You just use fixed-point arithmetic instead of floating-point (i.e. a fixed 32 bits of precision, or 16 bits, or whatever). A simple way of doing is is to make INT_MAX/2 = 1.0, -INT_MAX/2 = -1.0, and everything in between scaled appropriately. (/2 to avoid overflow). Then you implement fixed-point addition, multiplication, division, and subtraction (as commonly doing in hardware DSP chips) and you've got yourself an integer-only FFT.

Some really old C code doing something along these lines is available here.

Re:nope.

[TheRaven64]

Using SIMD is intrinsically easier than using a cluster. To use a SIMD instruction set all you need to do is isolate occurences where you are applying the same operation to multiple units of data and (in the case of AltiVec) call the corresponding vector operation in the standard lib.

Coding for a cluster introduces all kinds of communication and synchronisation headaches, especially since it takes such a long time to communicate between nodes (1ms is a very long time in terms of a CPU).