This is about an 8-9% Voltage tolerance, which is (unfortunately) normal with generic PSUs. Even though I frown upon this tolerence, as well as generic PSUs (unless one actually builds it his or herself and designed it as such), your differential voltage fluctuation (13.056 - 12.992) is normal. I'm running an AIW 9800 pro, and it may not draw as much (wattage) as a prescott, but I would never use a generic PSU from a store. If your happy with your generic, that's fine. But if something gets blown, you can bet that your generic PSU is a suspect, if not the prime suspect.