FUD Zilla heard at CeBIT that ATI's upcoming RV790 GPU is not simply a faster version of the RV770, it's a new 55nm chip. The new high-end card is expected to beat the GeForce GTX 260, and may even come close to the GeForce GTX 285.
The company didn’t want to postpone the introduction of the new card in performance segment and therefore did it in 55nm, while RV740 remains the first 40nm. RV740 just launched as a mobile chip, and we’ve seen it up and running, while the desktop part should arrive in the next month or two.
The new chip is a new architecture, but with some basic concepts taken from the RV770, that is why the chip will be significantly faster than anything based on the RV770. It is not just a speed bump and a better batch of RV770 based Radeon HD 4870 and 4850 chips, it is a newer and better chip.