At last ATI has the final Radeon HD 2900XT speeds. The card will work at 507 MHz in 2D mode and 757 MHz in 3D mode. ATI wants to save some power if you are not playing games all the time.
In 3D mode the memory works at 1656 MHz, while if you are just doing 2D stuff,f the memory will slow down to 1028 MHz. We are talking about the 512 MB GDDR3 card.
ATI found that these clocks have much better yield than the previous 800 / 1600 MHz combination. The cards with these clocks will hit retail and etail stores on the 14th of May.