I know info has already been posted about the upcoming 8600, but I wanna focus specifically on its 128-bit memory bus. Why is nVidia pairing their new GeForce 8s with such low bandwidth bus?
Nvidia's GeForce 8800-series graphics cards have generously wide memory buses, but their upcoming mainstream siblings may end up being a little more bandwidth-constrained. According to a report by VR-Zone, GeForce 8600 cards will have 128-bit-wide memory buses, just like their GeForce 7600- and GeForce 6600-series predecessors.
The site says Nvidia will introduce two GeForce 8600 models: a GeForce 8600 GT with a 650MHz core clock and 900MHz memory and a GeForce 8600 GS with 550MHz core and 700MHz memory clocks. Both models will have 64 stream processors, a 128-bit memory bus, and 256MB of GDDR3 RAM. Those specs contradict previous rumors, and they suggest the two cards will only have 28.8GB/s and 22.4GB/s of memory bandwidth—pretty low considering the GeForce 7900 GS has 42.2GB/s.
http://techreport.com/onearticle.x/11658