computer restart for no reason - suspect PSU problem

[CounterStrike]

Guys,

I have been using cgminer mining with 3 GPU (R9 280x) for about 3 weeks with seasonic 1000watt platinum PSU. But today it just restart my whole comp immediately when I start mining with 3 gpu but it work with 2 gpu. I only draw 780 watt from wall with 3 GPU so power isn't the problem. What can it be?

Thanks...

[vm1990]

heat?
or the motherboard cant handle 3 cards.
try 2 gpus and if it stays stable for a day or 2 then its either a dodgy card or more likely the motherboard or PSU is having trouble keeping up with the gpus

[zhinkk]

That does sound like a PSU problem. Is there another high wattage PSU you can try in that system?

[DrG]

I'm assuming you're doing scrypt coins.  Just clock everything to 0.9x multiplier the current value, but keep voltages the same.  If it's stable like that then you're clocking too high.

I would suspect the PSU only if it resets when the PSU is warmer like mid-day since it will draw more watts at that time.  My 4 card rigs would swing 50 watts depending on the time of day.