256bit Processors ?

[Hellmund]

I was looking up on 3dcards when I came across diamonds FireGL1, it has a 256bit rasteriser.Most GPU's have 128 bit processors so why don't they apply same concept to CPU's?

[SDT]

In order to do that you would have to replace the O/S with a 256 bit O/S. We know who has a strangle hold on p.c. O/S's so don't expect THAT to happen too soon.
The applications would also have to be 256 bit to take advantage of the chip so they would have to be rewritten too. I would expect that heat would be a problem as the chip density would be much greater in order to handle the 256 wide path. The other thing that "current" x86 cpu's have is backward compatibility... When the AS/400 went to 64 bit in 1996 the O/S had to be replaced and the applications had to be recompiled. I believe that the O/S that runs on the Alpha chip (64 bit) has still has not made the complete transition to 64 bit due to the complexity of the change.
I think that the net of it is chip density cost (the technology isn't there yet) and cost of rewriting mainstream applications. When the demand is there someone will find a way to do it because it will be profitable to do so.