PlayStation 3 chip has split personality

Engineers from Sony, IBM and Toshiba revealed those and other specifications for the Cell processor during a press conference at the International Solid-State Circuits Conference, where technical papers on the Cell design will be presented this week.

The three companies have been working on Cell for several years, promising to deliver a high-performance chip optimised for multimedia applications. Test production of Cell chips is set to begin later this year, and the processors will appear later in workstation PCs optimised for animation and other graphics chores. The chip will also power the next version of Sony's PlayStation game console, which is widely expected to be released late this year or early next year.

While analysts and researchers have already puzzled out most of the basic aspects of the Cell design, Monday's announcements included some of the first specifics.

Cell will have a 64-bit IBM Power processor and eight "synergistic processing units" capable of handling separate computing tasks, said Jim Kahle, an IBM Fellow. The Power processor will act as the brain of the chip, running the main operating system for an application and divvying up chores for the other processors.

The multicore design will give software developers tremendous flexibility, Kahle said, allowing them to run multiple operating systems on the same chip and experiment with variations on grid computing.

"It's designed from the beginning to work in a world where all the computers are tied together," he said.

Future versions of Cell chips could have more or fewer processing units depending on what device and software designers require, Kahle said. "There are a number of different ways to implement parallelism on the chip," he said.

How those processing units are used is up to software developers, including the game makers who will soon start wrestling with the PlayStation 3. Kahle said IBM and its Cell partners will provide game developers and other code writers with open-source tools and guidelines for working with Cell but that game developers will have final say on how they chop up computing tasks among the processing units.

"It's really...up to the game developer," he said. "You can program it in many different ways."

Other Cell numbers include the following.

ââ,¬Â¢ The first version of the chip will run at speeds faster than 4GHz. Engineers were vague about how much faster, but reports from design partners say 4.6GHz is likely. By comparison, the fastest current Pentium PC processor tops out at 3.8GHz.

ââ,¬Â¢ Cell can process 256 billion calculations per second (256 gigaflops), falling a wee bit short of marketing hyperbole calling it a "supercomputer on a chip." The slowest machine on the current list of the Top 500 supercomputers can do 851 gigaflops.

ââ,¬Â¢ The chip will have 2.5MB of on-chip memory and have the ability to shuttle data to and from off-chip memory at speeds up to 100 gigabytes per second, using XDR and FlexIO interface technology licensed from Rambus.

"One of the key messages you hear from the architects of next-generation chips is that their performance is being limited by off-chip bandwidth," said Rich Warmke, product marketing manager at Rambus. "We've really licked that with Cell. One hundred gigabytes per second is really unprecedented in the industry."

ââ,¬Â¢ The chip will have 234 million transistors, measure 221mm square and be produced using advanced 90-nanometer chipmaking processes. Peter Glaskowsky, a consultant at research company The Envisioneering Group, said he expects Cell production to shift to a 65-nanometer process, however, as IBM introduces the chipmaking technology later this year.

While the PlayStation 3 is likely to be the first mass-market product to use Cell, the chip's designers have said the flexible architecture means that Cell will be useful for a wide range of applications, from servers to cell phones. Initial devices are unlikely to be any smaller than a game console, however -- the first version of the Cell will run hot enough to require a cooling fan, Kahle said.

Some competitors, however, are sceptical that Cell will find much of a home outside of video games. One of the big problems with Cell, said Justin Rattner, an Intel Fellow, is that the processing units aren't identical, a situation that increases complexity and the opportunity for bugs.

"You've got this asymmetry," Rattner said. "It's like having two kinds of motors under the hood. We are very reluctant to adopt architectures like this because they take compatibility and throw it out the window."

CNET News.com's Michael Kanellos contributed to this report.