The current 9600 GSO features a G92 graphics processor with 96 stream processors, a 550MHz core speed, a 1375MHz shader speed, and 384MB of 800MHz GDDR3 RAM tied to a 192-bit memory interface. Expreview says the "updated" GeForce 9600 GSO will feature a G94 GPU (the one that powers the GeForce 9600 GT) with 48 stream processors, a 256-bit memory interface, and either 256MB or 512MB of RAM.

The wider interface could translate into higher memory bandwidth, and the 512MB card may perform better on account of its higher memory capacity, but the reduced stream processor count could adversely affect performance in spite of those upsides. Of course, one should be able to tell the old and new cards apart quite easily by looking at the memory size.

http://techreport.com/discussions.x/15660