VR Zone writes there will be 55nm and 65nm versions of the NVIDIA GeForce 9800 GT GPU. The 65nm will be a rebranded, but higher clocked, GeForce 8800 GT while the 55nm version will feature the new G92b core.
The 65nm version is actually a rebranded GeForce 8800 GT based on G92 core while the 55nm version is actually G92b core we have told you before. Both will be higher clocked than the 8800 GT.
The reason is that Nvidia is not comfortable to go full fledge 55nm process like AMD so the 65nm version is more of a safety precaution just in case the yield from 55nm doesn't turn out well.