you have a typo in the following paragraph:

The [b]four[/b] companies also announced that they would reveal technical details of Cell at the International Solid State Circuits Conference (ISSCC) to be held from February 6th to 10th , 2005, in San Francisco.

it should be The three companies...

There is a 4th. RAMBUS did help design one of the features in Cell chip (with some folks from Stanford).

From a specific standpoint, there's 5 players that worked on this chip. Or had involvement in designing part of it.