thx!
could your instability problem be a result of an insufficient PSU? with OC the cards draw up to 450 Watt each, and depending on your mobo, cpu and other things and the efficiency of your PSU this could cause the instability issues!
i know its the power, but its not my psu, my psu is 1500W. the instability is because i set high clock and low voltage (limited in ubuntu). i read some articles about 6990 overclock and they say for 1000mhz core it needs about 1.2v -1.25v. and in ubuntu amdoverdrivectrl its limited at 1.175v, thats max in ubuntu... i want to know if there is a way to increase voltage more then 1.175v in ubuntu... or should i use windows.