Memory Bandwith!!!

[fazz]

Ahem... you guys are breaking your heads too much. The original question could be answered like this:

"Sony, MS and Nintendo could've used a 256 bit memory interface instead of a 128 bit (64 bit in the case of the Wii) one. They could also use GDDR4 or GDDR5."

See? Simple. The original question has nothing to do with the Cell, the Xenos, or whatever.