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Ars Technica's Hannibal on IBM's Cell
endersdouble writes "Ars Technica's Jon "Hannibal" Stokes, known for
his many articles on CPU technology, has posted a new article on IBM's new Cell processor. This one is the first part of a series, and covers the processor's approach to caching and control logic. Good read."
Part II is up as well.
From the article:
The Cell and Apple
Finally, before signing off, I should clarify my earlier remarks to the effect that I don't think that Apple will use this CPU. I originally based this assessment on the fact that I knew that the SPUs would not use VMX/Altivec. However, the PPC core does have a VMX unit. Nonetheless, I expect this VMX to be very simple, and roughly comparable to the Altivec unit o the first G4. Everything on this processor is stripped down to the bare minimum, so don't expect a ton of VMX performance out of it, and definitely not anything comparable to the G5. Furthermore, any Altivec code written for the new G4 or G5 would have to be completely reoptimized due to inorder nature of the PPC core's issue.
So the short answer is, Apple's use of this chip is within the realm of concievability, but it's extremely unlikely in the short- and medium-term. Apple is just too heavily invested in Altivec, and this processor is going to be a relative weakling in that department. Sure, it'll pack a major SIMD punch, but that will not be a double-precision Alitvec-type punch.
Not quite. The Cell is 9 complete yet simple CPU's in one. Each handles its own tasks with its own memory. Imagine 9 computers each with a really fast network connection to the other 8. You could problably treat them as extra vector processors, but you'd then miss out on a lot of potential applications. For instance, the small processors can talk to each other rather than work with the PowerPC at all.
Hardly. Sony is following the same game plan as they did with their Emotion Engine in the PS2. Everyone thought that they were losing 1-200 bucks per machine at launch, but financial records have shown that besides the initial R&D (the cost of which is hard to figure out), they were only selling the PS2 at a small loss initially, and were breaking even by the end of the first year. By fabbing their own units, they took a huge risk, but they reaped huge benefits. Their risk and reward is roughly the same now as it was then.
Doubtful. The problem is that though the main CPU is PowerPC-based like current Apple chips, it is stripped down, and the Altivec support will be much lower than in current G5s. Unoptomized, Apple code would run like a G4 on this hardware. They would have to commit to a lot of R&D for their OS to use the additional 8 processors on the chip, and redesign all their tweaked Altivec code. It would not be a simple port. A couple of years to complete, at least.
This is half-true. While it will be hard, most game logic will be performed on the traditional PowerPC part of the Cell, and thus normal to program. The difficult part will be concentrated in specific algorithms, like a physics engine, or certain AI. The modular nature of this code will mean that you could buy a physics engine already designed to fit into the 128k limitation of the subprocessor, and add the hooks into your code. Easy as pie.
Bwahahaha! No way. This is a delicate bit of coding that is going to need to be tweaked by highly-paid coders for every single game. Letting on OS predictively determine what code needs to get sent to what processor to run is insane in this case. The cost of switching out instructions is going to be very high, so any switch will need to be carefully considered by the designer, or the frame-rate will hit rock-bottom.
This is one myth that could be correct. The Cell is huge (relatively), and given IBM's problems in the recent past with making large, fast PowerPC chips, it's a huge gamble on the part of all parties involved that they can fab enough of these things.