It appears like we will start hearing of Playstation 3 architecture a lot in the new year, though it's rumoured the console itself won't see the light until late 2004. First we have CNet News with the word that Sony and Toshiba have licensed some technology from Rambus, we never seem to be able to get rid of these guys:

Sony and Toshiba have licensed technology from Rambus that likely will be incorporated into a future version of the PlayStation game console. The two Japanese giants have licensed "Yellowstone," a high-speed interface for connecting memory to microprocessors, and "Redwood," a chip-to-chip connection, from the processor designer, the companies said.

The Inquirer goes a bit further onto specs detailing the processing power that might drive Sony's next generation console:

... He said that the computers are made of cells, each one containing a CPU, which will probably be a PowerPC, and eight APUs (vectorial processors) each with 128K of memory.
It will run at 4GHz, producing a not inconsiderable 256Gflops, with the cells connected to the central 64MB memory through a switched 1024 bit bus.

It's still not clear how many of these "cells" will be used in the Playstation3, but Sony reckoned some time ago it could be as many as one teraflops, probably making it a four cell architecture.