Nvidia confirms GT-200 with 1 billion transistors

[DilTech]

256bits + GDDR5 gives you more bandwidth.

Look to R600 at 512bits. The formule didn´t work.
The PCB is much more complex, the core is bigger, you have more bus stops inside the chip.

R600's formula didn't work because it couldn't USE the bandwidth. Too few rops, inefficient AA, too few tmus for AF... The rest of the architecture held it back.

Also, you realize you'd need roughly 4ghz GDDR5 at 256bit to match 2ghz GDDR3 at 512bit, right? Also, GDDR3 is likely to be lower latency than GDDR5 as well.