Prospects For the CELL Microprocessor Beyond Games

News for nerds writes "The ISSCC 2005, the "Chip Olympics", is over and David T. Wang at Real World Technologies put a very objective review of the CELL processor (the slides for the briefing are also available), covering all the aspects disclosed at the conference. Besides the much touted 256 GFlops single-precision floating point performance the CELL processor has 25-30 GFlops in double-precision, which is useful enough for scientific computation. Linus seems interested in CELL, too."

Comments

I'll believe it when I see it

[chris09876]

This is a very positive review for the cell processor. It does seem like a really exciting new piece of technology. It promises a lot, and if it will do everything people say it will do, it really has the possibility to give the entire industry a big leap forward.

That being said, I think it's important not to get too excited about it... it's hard to say if it will live up to everything that people have written about it. I'm a bit skeptical. Until I see some production units doing amazing things, I'm cautiously optimistic.

Re:I'll believe it when I see it

[BobPaul]

That being said, I think it's important not to get too excited about it... it's hard to say if it will live up to everything that people have written about it. I'm a bit skeptical. Until I see some production units doing amazing things, I'm cautiously optimistic

I'm a little bit concerned about the PowerPC Element. The article states that it's not simply a Power5 derivative, but a core designed for high mhz at the cost of per stage logic depth. To quote the author: "The result is a processing core that operates at a high frequency with relatively low power consumption, and perhaps relatively poorer scalar performance compared to the beefy POWER5 processor core. "

The means the PPE in the CELL @ 4Ghz will not perform as well as a Power5 would could it reach 4Ghz (but since the CELL has 8 SPEs, I would hope it performs better as a whole than a POWER5 at the same frequency). It would be interesting to know at what frequency the two are similar, but since the PPE is integrated into an extended system, this isn't something that can ever really be benchmarked.

What's the point?

[jeif1k]

Unless you are computing digital orreries, whether it has 256GFlops or 256TFlops makes little difference if the memory bandwidth isn't substantially increased, and people don't increase the memory bandwidth because that has expensive consequences all over the system.

On the whole, my impression is that current mainstream CPUs have a pretty reasonable balance between CPU power and all the other system components. Changing just the CPU without making substantial (and expensive) changes to the rest of the system will not magically give you more performance.

250 Gigaflops?

[CTho9305]

People seem to think this is leaps and bounds above everything else, but they're missing the details. In order to obtain that much performance, you'll need a task which parallelizes well so it can be broken up into chunks for the 8 SPEs. Graphics rendering falls into this set of tasks, but a lot of general applications just don't gain that much from parallel processors. Even when you have a task that does parallelize, writing parallel code is quite a bit harder than writing code for just a single thread of execution.

I've seen a lot of hype about having the Cell in your laptop talk to the Cells in your desktop, microwave, and TiVo, but you have to consider real-world limitations. When you set up a network like that (presumably wireless), you're going to be limited to around 100Mbps. In computer clusters and supercomputers, one of the main limitations of performance is the communcation bandwidth available between processors, and the latency of the network. To build a "home supercomputer", you not only need a task that parallelizes well, but one that doesn't require so much inter-node communication that it's held back by a slow network. You can't work around this problem with hardware magic - if the task you're working on requires lots of communication bandwidth, you're going to be held back.

So how much beyond a modern PC is 250GFLOPS anyway? Not much! A GeForce FX at 500MHz does 200 gigaflops. An AMD Athlon's peak performance is 2.4 GFLOPS at 600 MHz... if we scale this up to 2.2 GHz (high-end Athlon), that's 8.8GFLOPS (note: As we're talking about theoretical performance, nonlinear factors like bus speeds can be ignored). Basically, if the Cell dedicates most of its power to graphics rendering, you'll have computation power in the same range as a fast PC of today. Given that we're not going to see any products based on the Cell for a while, this isn't going to be the end of the world for Intel and nVidia (let alone the fact that Cell isn't x86).

Consoles using the Cell will have the advantage of only having to render for TV resolutions - at most 1080 lines, while PCs will be rendering at up to 1600x1200, but if you look at recent history, you can compare the xbox to a then-good PC with a GeForce3 (which came out at around the same time) - the xbox looked better, but PCs did catch up and surpass it's performance and it didn't take all that long. Consoles have to be very high-end when they're released, because the platform doesn't change for 2-3 years, and they still need to be "good enough" after a couple years, before the next generation is released.