Cell Inside, the Future of Processor Architecture

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A few days ago, IBM explained that they would open the design specifications and software libraries for their Cell processor, which is still in development. The Cell processor represents an incredible leap in computing technology, and it is debuting in the consumer market next year inside the Playstation 3. So how is the Cell processor so different from AMD’s and Intel’s x86 chips? And what is so significant about opening up the hardware?

The Cell Processor

The Cell processor is being developed jointly by Sony, Toshiba, and IBM. The first two are obviously interested in its multimedia capacities, which look like they will be stunning. The last, IBM, is a good member to round out the group due to their background in manufacturing large volumes of high-end processors.

To demonstrate the capacity of the unfinished Cell, Toshiba released a video in April of a computer decoding 48 streams of video simultaneously. The screen was divided into a grid of thumbnails at 1920x1080 resolution, each playing a separate SDTV mpeg-2.

Needless to say, this is a little more than my own modest Athlon could ever handle. To use this multimedia power, Toshiba plans to install these chips into upcoming TVs. Yet this demo doesn’t demonstrate what the processor could do for computers, which is obviously where the chip is creating a buzz.

Earlier this week, IBM agreed to lisence Cell to Mercury Computer Systems Inc. Mercury says they expect Cell to be three to four times faster than rival chips that are scheduled to be released in the next few years. Mercury produces medical and military equipment, and they plan to use Cell for a wide variety of applications, from missile radar systems to magnetic resonance image (MRI) scanners.

Sony’s upcoming Playstation 3, coming out next year, has been known already to be the debut of a consumer Cell product. It might give everyone an idea of how well an early Cell system can crunch numbers and render polygons.

So How Fast is It?

So far, current processors from AMD and Intel are having trouble pushing the 4 GHz mark, a mark Cell is easily clocked past. The PS3 at the E3 2005 demo has a Cell clocked down to a stable 3.2 GHz, providing 218 GFLOPS of power (and the graphics card in the PS3 provides 1.8 TFLOPS). It's also impossible to say what features have been removed or simplified in order to get this version of the Cell chip ready soon. However, Cell development is clocking it at 4 to 4.6 GHz, and is reported to have clocked it as high as 5.6 GHz. Of course, clock speed is not the only factor in a processor's performance, so don't take these figures as anything conclusive.

Altogether the Cell processor is a crowded little chip, with a whopping 234 million transistors (compare to AMD64’s 114 million transistors). The potential processing power of Cell blows away existing processors, even supercomputers. One Cell working alone has the potential of reaching 256 GFLOPS (gigaflops, processing 256 billion floating point operations per second). GFLOPS are benchmarked with a program called Linpack and are mostly usefull for comparing supercomupters. To compare, your home PC would be extremely lucky to reach 6 GFLOPS, unless you count your graphics card. This isn't to say that GFLOPS on the Cell and on your home PC provide an accurate way to judge exact performance specs. It's more of a cursory comparison.

The world’s 500^th fastest computer (registered on http://www.top500.org) is a SuperDome by Hewlett-Packard. Most supercomputers use arrays of many machines, and the SuperDome array only reaches 850 GFLOPS. A handful of Cells could put it to shame. Of course, to make a balanced comparison, the fastest supercomputer is currently IBM’s BlueGene/L running at 70720 GFLOPS. Supercomputers should eventually make use of Cell architecture, stacking these processors to blow away old processing records. In fact, Cell is specially engineered to work cooperatively with other machines.

Though there aren't really any more Cell demonstrations, there is plenty of information on the general structure and capabilities of the chip. The most outstanding difference between Cell and current technologies is that a normal CPU in a computer or game console has, of course, one processing unit that churns through one thread of data. Cell can run through many threads of data at a time through the eight (that’s right, eight!) data processing units within a single chip.

Next: Cell Architecture >>
 

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