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.
AMD expects that PC graphics will benefit from the increase in memory bandwidth for a variety of intensive applications. PC gamers will have the potential to play at high resolutions and image quality settings, with superb overall gaming performance. PC applications will have the potential to benefit from fast load times, with superior responsiveness and multi-tasking.

AMD is working with a number of memory providers, including Samsung, Hynix, and Qimonda, to bring GDDR5 to market.
AMD did not reveal yet what new ATI card generations will be GDDR5 powered and when these cards will be available. The rumors say that the ATI Radeon 4870 will support DDR5 memory slated for the end of June.