Quote Originally Posted by Nintendork View Post
256bit*5700Mhz GDDR5 = 182.4GB/s
384bit*3800Mhz slow GDDR5 = 182.4GB/s

With GDDR5 there's no reason to increase bus width unless you have an inefficient memory controller that can't handle high speed GDDR5 such as nvidia. Just with that a chip cost more-take more space in die --> bigger die- for the same performance.


I see you are new to AMD arq improvements. See Barts HD6800 for example. Cayman brings even more efficiency than Barts.


PaganII
You already can with any HD6000.
You forgot one minor tid-bit... The slower GDDR5 generally has tighter timings. As such, with both at the same bandwidth over-all the wider-bus will generally end up the faster, albeit by what amount this effects things remains to be seen.