Today AMD announced the first commercial implementation of GDDR5 (Graphics Double Data Rate, version 5) memory in its forthcoming next generation of ATI Radeon graphics cards.

The GPU performance in today's graphics cards is limited by the rate at which data can be moved on and off the graphics chip, which in turn is limited by the memory interface width and die size.
The higher data rates supported by GDDR5 is up to 5x that of GDDR3 and 4x that of GDDR4