Both listed cards run at 850MHz for the core, which is 100MHz higher than the RV770 based HD 4870. Memory has also been bumped up from 900MHz (3600MHz effective), to 975MHz (3900MHz effective). The stream processor and texture unit count stays the same, 800 and 40 respectively.

http://www.fudzilla.com/index.php?op...60&It emid=34