i have duel 7900 gtx's and when windows loads up the pc automaticly reboots about 5 seconds after i can see my desktop..
it wont stop doing this until i go into system's device manager and disable the second card while in "windows safe mode"... but after i do that i restart with only one card running and it boots up fine and then i can enable the second card after the pc is running..
my question is what conflict is causing something like this to happen? its real annoying disabling my second video card before i shut down my pc just so it boots up without problems in the morning..
With Prozac. Gotta to be the PSU. FSP, Antec, TT are all good. I'm sure I've missed some good makers, but those come first to my mind. I'd say 550W+ just to be safe, but just make sure you have 35A+ combined total on the 12V rail. What are the amps on the 12V+ on your current PSU?
More important than volts or watts is amps but people don't seem to take that serious enough. It does you no good to have a high wattage PSU if it doesn't provide for a sufficient amperage across its rails against the draw. I used an FSP 700 with my XFX 7900 GTX Extreme and it had issue powering the card. XFX Tech Support told me that the amperage across its rails wasn't enough. So, I replaced it with a Silverstone 750 and everything has been great since. With that in mind, don't get something with less that 17 amps across it's rails or you'll just be back here with the same issue.
Here's a review of highend PSUs that will give you some insight as to their stability:
Enermax 535W Whisper II EG565P-VE FMA V2.0 - SLI Ready
Model: EG565P-VE FMA 2.0
Maximum Power: 535W (support both 24pins and 20pins motherboards)
Input Voltage: 90V~135V or 90V~265V
Input Frequency Range: 47Hz~63Hz
Input Current: 40A/115V and 80A/230V max. during cold start
Hold-up time: 17ms at 115VAC or 230VAC, full load
Over Voltage Protection: +5V: 5.5V~7.0V; +3.3V:3.76V~4.3V; +12V & +12V2: 13.4V~15.6V
Over Load Protection: 110~160% of max load
Over current Protection: +3.3V: 55A (max); +5V: 48A (max); +12V1 & +12V2: 20A (max)
Over Temperature Protection: Operating Ambient 10ºC~40ºC, Storage Ambient -40ºC~70ºC
Operating: to 85% relative humidity, non condensing at 25ºC
Storage: to 95% relative humidity, non-condensing at 50ºC
MTBF: Greater than 100K hours at 70% of full rated load; 230VAC / 50Hz input; 25ºC ambient
EMC: EN55022 Class B, EN61000-4-2 Class B, EN61000-4-3 Class A, EN61000-4-4 Class B, EN61000-4-5 Class B, EN61000-4-6 Class A, EN61000-4-8 Class A, EN61000-4-11 Class B, FCC Part 15 & Part 2, CNS 13438 Class B
Safety: Approval UL, cUL, TÜV, CB
Dimension: W150 x H86 x D140 (mm)