A lot of nonsense has been talked about the Cell processor. That it will gazump every CPU on the market one hundred times over, that it will change the computing world forever, that it can make a cracking chip butty… but fact should start to emerge from fiction now its trio of big name developers (IBM, Sony and Toshiba) have released details of its architecture to the public.
Available here, there’s over 330 pages of technical explication split into five categories: Cell Broaband Engine Architecture, Synergistic Processor Unit (SPU) Instruction Set Architecture, SPU C/C++ Language Extensions, SPU Application Binary Interface Specification and SPU Assembly Language Specification. A better man than me will understand their content. (I went for the fair more straightforward two page synopsis, courtesy of Dr.H. Peter Hofstee of IBM, which is available here).
Ultimately, however, the unabridged documents will form a backbone of knowledge for software programmers and hardware developers as the Cell looks to expand its use beyond the initial implementation in the upcoming PlayStation 3 games console and onto larger platforms such as enterprise level servers. The reason for this is because, despite being essentially an evolution of the PowerPC it has an incredible nine processors onboard operating on a shared coherent memory making it easily scaleable.
So what are these processors? Today’s documentation explains that one is the Power Processor Element (PPE) and eight are Synergistic Processor Elements (SPE). The PPE is a 64bit Power Architecture core and is backwards compatible with 32bit systems and applications (including Mac OS X), while the SPE is optimized for running compute intensive apps rather than an operating system. The principle behind this design is to get around memory latency which, in recent times, has been more of a bottleneck to performance than the processor itself. “The result can be compared to a bucket brigade in which a hundred people are required to cover the distance to the water needed to put the fire out, but only a few buckets are available," said Hofsee.
Time will tell whether the Cell’s innovative design gets around such current day problems as well as the developing trio believe, but at least the stage is set for the market to be enlarged beyond the turgid AMD and Intel catfights. So after four years in development we get 330 pages to read just as a Bank Holiday Weekend begins… Shall we read it? Nah, not right now!
You can find specific details on the version of the Cell Processor used in the PlayStation 3 here.