Xenon and Revolution CPUs: PowerPC 970 vs Power5 ?

[archie4oz]

Sorry, perhaps I should've said "single-cycle execution"...

Also I'm getting the impression that you're in a real x86 implementation logger right now... Most of the little RISC designs you see in consoles have REALLY shallow FPUs... Hell the Power4/970 (and I guess now Power5) is the exception not the rule for PowerPC)...

 

[DeanoC]

I agree with Archie, 970 or Power5 aren't console CPU's.

Given 2 options I always pick the third

 

[Fafalada]

But it doesn't take a single cycle for the FPU to complete the operation from start to finish. Float execution unit is typically even deeper pipelined than the integer execution unit...

Not in your average Risc cpus. Most instructions (especially all the elementary operations like Mul/Add/MAdd etc.) are normalized for latency/throughput, and typical FPU pipelines are rather short too (750 series is 3stages for FPU for instance).

And the few abberations there are that break the normalized latency rule(like Div, and various complex trigonometric and other operations if implemented on the FPU) typically all have much slower throughput anyhow so they don't break anything as far as throughput goes.

 

[Brimstone]

I agree with Archie, 970 or Power5 aren't console CPU's.

Given 2 options I always pick the third

Well if Microsoft wants a CPU with a tremendous floating point performance, they should get a PIM design. The most famous type of PIM design IBM has is Blue Gene/C also refered to as Blue Gene Cyclops. Micron with it Yukon PIM design would have delivered a more than half a terraflop of floating point per chip.

Micron didn't see its Yukon PIM design as a replacement for a standard CPU, more of a supplement where a developer could utilize the extreme bandwidth and parrelism for certain problems. Have a standard CPU, PIM CPU, and VPU.

 

[ERP]

Ahhh but it's not just about the flops........

Traditional AI for example is mostly about searching problem spaces, hardly a flop in sight, it'a all about how fast you can access the data.

I predict that the balance between AI and rendering is going to be very different in the next generation of consoles than it was in this one. Assuming one of the manufacturers doesn't cripple their CPU and make it impractical.

 

[Megadrive1988]

I realized last night that I still find myself confused on the Xbox 2 CPU configuration.

I re-read some of the articles on Xbox 2 from the last few months.

I called the Xbox 2 CPUs PowerPC 970 mistakenly I think. from the articles, it's supposed to be a newer core, the 976, which is meant to be the first dual core (true dual core) PowerPC, as it is derived from the POWER5. these might be in future Mac G6 computers. there's supposed to be on 65 nm and out in 2005/2006.

now comes the confusing part for me. if these 976 cores are true dual core, why wouldn't they be able to process 4 threads each? maybe that ability is being removed from the consumer version? otherwise, wouldn't Xbox 2 be able to process 12 threads instead of 6? (3 PowerPC 976 dual core CPUs)

 

[Guden Oden]

PPC976 isn't derived from Power5 to my knowledge, but an evolution of the PPC970. Developing a CPU is a tremendous effort, you don't just throw away a design after one generation and do another like with 3D cards. The effort that has to be put into troubleshooting and bugtesting these extremely complicated designs are nothing but staggering.

Look at what AMD and Intel is doing. Intel is still evolving the P6 core (debuted in 95), and AMD the Athlon (99 I believe). That IBM would throw away their CPU after just a year is something I consider completely out of the question.

 

[archie4oz]

I called the Xbox 2 CPUs PowerPC 970 mistakenly I think. from the articles, it's supposed to be a newer core, the 976, which is meant to be the first dual core (true dual core) PowerPC, as it is derived from the POWER5. these might be in future Mac G6 computers. there's supposed to be on 65 nm and out in 2005/2006.

now comes the confusing part for me. if these 976 cores are true dual core, why wouldn't they be able to process 4 threads each? maybe that ability is being removed from the consumer version? otherwise, wouldn't Xbox 2 be able to process 12 threads instead of 6? (3 PowerPC 976 dual core CPUs)

Probably because you're relying on worse speculative information than the typical Mac rumour site would have...