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duel 7900GTX's crash at start up

Last response: in Graphics & Displays
July 31, 2006 3:05:02 PM

Ok so heres the problem...

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..

any help would be great..
July 31, 2006 3:15:16 PM

What's the power supply?
July 31, 2006 3:16:54 PM

some 500 watt brand

should be plenty..
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July 31, 2006 3:18:54 PM

No, it's not enough. 500W on any crappy PSU will kill your system. Go invest like $80 in a good Fotron SOurce power supply, or Antec, or Enermax.
July 31, 2006 3:21:16 PM

what wattage should i go with? i didnt think sli would use that much more power..

on another note i had the 800 watt picked out for this system.. but the guys at ibuypower said i didnt need it.. and told me to got with the 550 watt
July 31, 2006 3:24:19 PM

500W isn't an issue, you can might (if really try), run SLI on a 450W PSU. It's the quality of the PSU that counts.
July 31, 2006 3:37:11 PM

so your thinking its not a software/driver issue and more of a poor quality product issue?
July 31, 2006 3:40:10 PM

Drivers are not causing anything, it's the power supply.
July 31, 2006 4:09:37 PM

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?

Try with one GTX and check the rails.

July 31, 2006 5:13:44 PM

thanks for the help guys
July 31, 2006 7:36:31 PM

Agreed, i have 2 as well and they eat up that power. I have a Aspire 680w with PFC, but doesnt offer that SLi feature(like it matters) Try antec,TT or OCZ, good brands overall.
July 31, 2006 8:01:16 PM

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:
July 31, 2006 8:57:40 PM

I'm running a single 7900gtx on ultra X2 550, but for SLI you might want 600+ or you could try one of these.

fits in a 5.25" drive bay and runs only the video cards, you might be able to keep the no name PSU you have now if this was added. There's also a 300W version made by somebody else.
July 31, 2006 10:23:56 PM

thanks alot guys, got a new one on its way
July 31, 2006 11:51:59 PM

this is what im using now

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)
Voltage Rails:
+12V: 34A
+12V1: 18A
+12V2: 18A
-12V: 0.8A
+5V: 32A
+5VSB: 2.5A
+3.3V: 32A
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)

im guessing i need more power..
August 1, 2006 12:39:16 AM

Well it has healthy amps, which is good. For something like a 7900 GTX SLI rig you don't dare use anything with less than a 17 amp average across its rails.

What are the rest of the components in your computer going to be? If you could give your system specs it would be helpful.