Future Power "Cell" Chip Will Probably Run Linux--And Well
by Timothy Prickett Morgan
Is the next wave of change in the IT market (specifically for processor chips) going to come from the game console of the future? It sure looks like it. IBM, Sony, and Toshiba have been collaborating on a massively multi-cored processor called "Cell" for the past three years, and last week the three companies divulged some of the details in the Cell chip's design and when we can expect to see it come to market.
The Cell chip is, like Sun Microsystems' future "Niagara" and "Rock" processors, a radically different design from the monolithic microprocessors that are used in PCs and servers today. While IBM, Sony, and Toshiba are talking a bit about Cell this week, the companies are not planning to give out all of the details on the chip until the International Solid State Circuits Conference in early February 2005. The Cell team is talking only because the papers submitted to ISSCC have set tongues wagging.
A lot of people have been guessing what Cell might look like based on some pretty thin information. Here's what the three Cell partners will cop to. At the heart of the chip is a single core based on IBM's 64-bit Power designs. Wrapped around this core will be what they call "multiple synergistic processor cores," whose job it is to deliver massive amounts of floating point processing power. Consumer electronic devices like HDTVs and game consoles are manipulating streaming video and audio in real time, and to do so they need to do a lot of calculations for high resolution images and high fidelity sound.
The IBM Power4 and Power5 processors all have two floating point units per core, and to create these synergistic cores, IBM may simply be cookie-cutting these FPUs and putting a lot of them at the disposal of the main CPU core in the Cell complex. But it looks like IBM has doubled down on the FPU cores, with four FPUs and four integer units each inside these synergistic cores. As is the case with the Power4 and Power5 chips, the Cell chip will have an I/O interface on its chip, but it appears to be of a radically different design based on Rambus memory and running as high as 6.4 GHz.
Exactly how many CPU cores and how many synergistic cores will be integrated into a single Cell chip is unclear, but the rumor is that each Cell CPU will have eight synergistic cores plus a direct memory access (DMA) controller all residing on a set of Rambus serial links between the elements. Eight of the synergistic cores would deliver 64 floating point operations per clock, and running the whole shebang at 2 GHz (a very reasonable clock speed for a big chip using IBM's 90 nanometer SOI chip technology) would deliver 128 gigaflops of performance. Cranking the clock speed on the Cells up to 4 GHz and putting four of these Cell chips into a single system (such as a Linux workstation or a HDTV set), would deliver 1 teraflops of computing power, which is a decent amount of oomph for a four-way server.
IBM and Sony put out another press release that said a one-rack workstation (which most of us call a server) using the Cell architecture could deliver as much as 16 teraflops of computing power. Such a machine would probably have to use 65 nanometer chip technologies (which Sony and Toshiba are helping IBM develop as part of the Cell project), and there would have to be a lot of the Cell chips in that box. If the Cell chips look anything at all like the speculation above, it would take around 64 Cell chips and their adjunct cores running at 4 GHz to deliver those 16 teraflops, or 48 Cell chips running at 6 GHz (which seems like an unlikely possibility given the heat issues). Sony has been bragging that it could deliver 1 teraflops of performance in a single Cell chip since 2001, but this does not seem possible.
The Cell architects, who work from a design center in Austin, Texas, that was set up with a $400 million budget back in 2001, say that the chip will support PC and workstation operating systems (notably Linux) as well as operating systems currently used in consumer and game devices (increasingly Linux). IBM will start production of the Cell chips during the first half of 2005 at its 300mm, 90 nanometer copper/SOI chip fab in East Fishkill, New York. IBM and Sony are developing a workstation based on Cell chips, which is the first product that IBM will ship based on the products. This workstation will apparently be aimed at game programmers and digital rendering houses. Sony plans to launch a line of home servers and HDTVs that use the Cell chips in 2006 as well as its computer entertainment center, which represents the merger of TV and PC with broadband networks and wireless devices. The Cell chip will eventually be at the heart of the PlayStation 3 game console, too, but Sony did not say when to expect it. Earlier this year, Sony ponied up another $325 million to help IBM work out the kinks in the 65 nanometer chip processes it is developing. The Japanese consumer giant has licensed IBM's chip technology and will be using it in its own 300mm fabs in Nagasaki to have an alternate source for Cell chips. Toshiba says it has a diverse line of products that will be Cell-based, and that it will start with an HDTV unit in 2006.
Sony and Toshiba are not the only companies adopting funky Power processors as the core of their game consoles and consumer devices. Earlier this year, Microsoft chose the Power chips for its future "Xenon" Xbox game console. Not much is known about the Xenon machines, but the rumor is that the Xenon chip will have three PowerPC cores on a single chip, running at 3.5 GHz. The machine is supposed to have 256 MB or more of main memory, an integrated graphics card with 10 MB of its own memory, and two separate vector processors built in as well. It is a good guess that Microsoft chose three stripped-down PowerPC 980 cores for the Xenon chip with processors similar to the synergistic cores in the Cell chip as vector processors. |
