Default memory voltage: 7900GTX = ~2.15V
Default memory voltage: 7900GTO= ~1.82V
Only difference is these two resistors
Attachment 52079
Vmem mod and read point. Best method is "red", but use turquoise if you don't want to solder. (I do not recommend "blue" method. There may be problems over 1.95V)
Attachment 52507
Vgpu mod and read point:
Attachment 52508