I have been running my Celeron 366 at 550 for a year now on a SOYO 6BA+IV at 2.0 volts at no higher than 108F at full load with case on and 104F with case off and it seems to be fully stable. On a side note, was able to get it to run 605 with same voltage for a while, then it would lock up. I didn't try higher voltage cuz I am trying to keep the temp down, so I don't end up with heat related problems on other parts in system, mainly cuz I gots a crappy enlight case with only one fan :-{