Hi. I was using gigbyte x58a-ud3r for last 1.5 years without any big problem. 2 days ago I changed my GTX460 to new GTX580. When I turned on computer it started but turned off and on itself before boot. I was doing same thing sometimes so i thought it is ok. Also my PSU is 700W, so i didn't think there is problem. after couple hours I played suddenly it turned off itself and since i cannot turn it on it just starts and after 3-4 seconds it turn off. So later when i search on internet about problem. I found out about PSU. I did not know that also A on the 12V is important. I checked mine and it was 18A and 580 needs 40A min.