We spotted many reports and photo's already with info on the upcoming RV790 release from ATI (Radeon HD 4890).  As seems now the GPU clocks on that product will get specced at 850 MHz. There however is a lot of stuff happening.

It looks like the board partners will do a lot of customized models, and apparently some of them can even reach a core clock frequency of an astounding 1.00 GHz.

On a Chinese tech forum PCInLife they have shown that the RV790 rather reached the 1 GHz mark, easily.

The overclocker reached speeds of 1 GHz (core) but that didn't stop right there. The reference memory clock frequency will be 3900 MHz right, well the overclocker reached 1125 MHz (=4.50 GHz effective, memory). To proof a point, this card ran 3DMark Vantage on eXtreme settings.

The X-mode returned a a score of X5480. That's smackdown right in-between the GeForce GTX 280 and GeForce GTX 285. Considering they had to be using a Beta driver, in combo with official drivers performance might be even a tad better.

Click on the image to enlarge btw.