Bandwidth is important , like GDDR3 -0.8ns ( use on 8800 Ultra ) had 2.5Ghz DDR , but GDDR5 will start at 3.5GHz ~ 4GHZ DDR . Just compare and you'll see who is faster . GDDR4 only ( until now ) used on 1 product which is Radeon X1950 XTX , so pity