The head of Toshiba's semiconductor operation, Yasuo Morimoto, has revealed a few further details of Cell - the multiprocessing-oriented CPU architecture for the broadband era currently being developed by Toshiba, Sony and IBM.
The three partners announced the chip earlier this month. They committed themselves to spending $400 million over the next five years developing the chip, described by Sony's Ken Kutaragi, the creator of the PlayStation, this way: "With built-in broadband connectivity, microprocessors that currently exist as individual islands will be more closely linked, making a network of systems act more as one, unified 'supersystem'. Just as biological cells in the body unite to form complete physical systems, Cell-based electronic products of all types will form the building blocks of larger systems."
Hard technical specs. remain few and far between, but Morimoto, speaking in an interview with the Nikkei newswire, does give a more detailed - albeit in a rather vague fashion - picture of the processor than the one presented at its launch.
As Morimoto describes it, Cell is a customisable architecture capable of being modified according to the needs of specific applications. Essentially, the CPU has a modular design - Morimoto calls it a "building block structure" - allowing chip makers to strip out features not necessary to the application they're working on. If they switch in all of all the chip's capacity, they'll be able to wring more than one teraflop of performance out of it, he says.
Morimoto also talks of the chip's "signal processing portion". Since this portion is said to be scalable, we reckon that's probably some kind of programmable vector processing engine.
The one consistent component of Cell's modular design is the I/O section, which will be standard across all Cell derivatives, Morimoto says, whether they're targeted as cellphones or large-scale servers, which itself gives an idea of the range of applications the three partners see the broadband-oriented CPU being implemented for.
Physically, Cell CPUs will have "packages with many pins and large chip sizes", according to Morimoto, but presumably that refers to the full-feature set version, since that's clearly not the description of a mobile-oriented processor.
"As the Cell chip size will be fairly large, the Cell chips are most suitable for being manufactured at the 300mm wafer facilities," he added.
Morimoto is tight-lipped on the subject of operating systems, saying only that it "will be an operating system that enables the Cells being connected to each other to operate in parallel". It also has to be capable of being scaled from very small mobile devices to high-end servers, if we take his comment about the applicability of the chip's I/O infrastructure at face value.
IBM, Sony and Toshiba are also developing peripheral chips, and there's even the tantalising hint that the three are developing a new memory system for the CPU, though it may simply be the interviewer reading too much into Morimoto's comments. From the sounds of it, we'd expect the CPU to use a NUMA-style memory infrastructure, providing each chip with access not only to its own memory space but to the RAM banks of others, possibly even down to the L2 cache level.
Interestingly, unlike Sony, Toshiba hasn't licensed IBM's copper, low-K dielectric and silicon-on-insulator manufacturing processes. It's going to use those technologies to build Cell, but it's developing them itself, says Morimoto. "It is not necessary to have the same process, but it's an essential condition for us to standardise the basic electric characteristics," he said.
The three companies have already said Cell will be fabbed at 0.1 micron. ®
Nikkei's interview with Yasuo Morimoto