AMD has been building both its RV670 and the new RV770 GPU on TSMC's 55nm process for a while now, but it wasn't until recently that Nvidia caught up by quietly die-shrinking its G92 GPU on the GeForce 9800 GTX+ cards. As it is to be expected Nvidia has more 55nm GPUs up its sleeve and, according to DigiTimes, four or five of them will come out this quarter.
In addition to Nvidia's GT200 and G92b GPUs that have already adopted a 55nm process, G94b, G96b, and G98b models will supposedly launch after August. The G94b should be a die-shrink of the G94 that powers GeForce 9600 GT cards, while the GeForce 9500 GT series is expected to launch with a 65nm G96 core in its first iteration by the end of this month, followed by a 55nm G96b variant later on. As for the G98b, it may supplant a GPU that hasn't even materialized just yet.
The move to a 55nm process will reportedly help lower manufacturing costs by as much as 20 percent, which should help Nvidia counter AMD's aggressive pricing strategy.