At ISSCC this week, IBM, Sony and Toshiba presented some papers on the Cell chip. Sony plans to use Cell as the core of its Playstation 3 console. But the three companies are promoting Cell as a “supercomputer on a chip”, to be used in a wide range of consumer and communication products.
The news media has largely repeated IBM’s press releases with the same breathless claims. The Merc gushes in New chip called a threat to Intel: “The partners say the first Cell chips, which can simultaneously juggle multiple computing tasks, will have 10 times the processing power of comparable Intel chips. Eventually, the technology could pack the power of a supercomputer in a handheld device.”
Right. Maybe a handheld device with a heat sink the size of a toaster.
According to the folks at CNet:”While IBM didn’t disclose the exact heat statistics, some at ISSCC said it could run as hot as 130 watts…. Cell contains 234 million transistors and takes up 221 square millimeters in the 90-nanometer process. That’s about double the size of the 90-nanometer 3.6GHz Pentium 4.”
That’s a big, expensive chip, built in a new, low-yield process. It also contains a new proprietary Rambus memory interface, further inflating system cost. As CNet points out, that might not matter to Sony, selling Playstation at a loss, but it might severely limit use of Cell outside of the console market.
More worrisome for me is the implication that Cell requires an entirely new programming model to effectively make use of that power.
Cell is a System on Chip (SOC) design, containing 8 vector execution units, and control processor based on PowerPC. It supports multiple threads of execution, and is supposed to run at 4 GHz in IBM’s new 90 nanometer Silicon on Insulator (SOI) technology. Naturally, the developers claim it will have “10 times the performance of PC processors”.
OK, Cell is certainly an interesting architecture. But listening to the claims reminds me too much of the past 20 years I’ve spent working on multiprocessor systems. Often it’s much easier to build innovative hardware than to get good performance out of those systems. And any system that requires substantial changes in how programs are written is a long shot.
[...] IBM has licenced their Cell processor to Mercury Computer Systems for use outside of gaming consoles. IBM Makes Progress On Cell Chip Strategy: “Mercury Computer Systems will use the Cell chips in computers that it makes for the medical imaging, defense, and seismic processing markets.” [...]