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Old April 28, 2009, 05:31 AM
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Default Power Supply for 2 x 8800 GTX in SLI

Hello,

I think I have to replace my 700W PS b/c in the middle of certain games (DoW2 and WoW) my computer is just cutting off. I mean everything in the case as if someone had just come and flicked the power switch. So Iím thinking of going with an OCZ 850W but Iím not sure if thatís enough for my 2 cards running in SLI mode. Any suggestions?

Thanks.
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Old April 28, 2009, 05:50 AM
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An 850W is usually more than enough.
Might be because that thing has a wierd Rail Setup.


Usually for help, we would really appriciate a Full System Setup, with All cooling options listed as well please! :)
That makes it much easier for us to help you out!

Best Regards,
ST
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Old April 28, 2009, 06:14 AM
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Sorry about that. I’m actually posting on my brother’s behalf and can’t remember what he has in his system. I know he has the 2 x 800 GTX cards in SLI, Dual Core CPU, 1 x HDD, Optical drive, and some memory. Nothing too fancy really. No RAID and no extra cooling other then a few additional fans on the case. So pretty plain. I know that whenever he plays those games though the system will periodically shut down completely. Which is why I think he 700W PSU is not enough. Anytime there is a demand for more power, it just cuts out. I think the 2 cards are putting a strain on the PSU which is why I’m hoping the 850W PSU will solve the problem.
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Old April 28, 2009, 06:39 AM
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I would suggest running one of those Video Card Benchmarking Programs to MAX out the Cards and see if you can reproduce the Shut Down once they start drawing full power.
3Dmark, Furmark etc etc...

Regards
ST
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Old April 28, 2009, 09:26 AM
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Pc p&c 750w
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Old April 28, 2009, 09:34 AM
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i ran 2 9800gtxs with a ocz 780watt. ran wihtout issued for a few months then changed setup
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Old April 28, 2009, 09:49 AM
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My current set up involves a pair of 9800GTX+'s, 6 HDD, 1 optical, and a Q9450 running at 3.6ghz. All on a Corsair HX750 (750 watt, single rail).

I have NEVER seen my UPS deliver more than 440W to my power supply, so I figure my components are never using more than about 380W..

I would say either your PS has different rails that are individually getting overloaded or (more likely) you're having overheating issues. Some older intel chips have a thermal switch on them. Open up the box and give it a good cleaning, and then throw a good aftermarket cooling solution on the processor. I recommend the OCZ vendetta II.

Good Luck!
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Old April 28, 2009, 09:59 AM
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I'm not familiar with the rails that are being referred too. Single rail?

Also, I know that the system has recently been cleaned out but now I'm wondering if it may be an overheating issue. Although I've seen overheating before and ususally things just crash or freeze up....this is shutting the computer down completely....exactly like flicking the power switch.
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Old April 28, 2009, 10:33 AM
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from a good PSU 700 watt is enough for your system, take a look at this, sicne they are a PSU vendor, I am sure they go on the cautious side of things :
Welcome to Corsair :: Power Supplies

they seem to recommend a 750 Watts....

I had an issue where my north brige was heating up, and it did freeze for about 2-3 second, then just power down. So, overheating issue can cause different situations.
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Old April 28, 2009, 11:45 AM
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I ran a pair of those for a while on a corsair tx650 with no problems. The MAX power draw from an 8800gtx is 185W. 370W total from both (they will NEVER actually draw that much, that is just Nvidias TDP for the card). CPU, HD, fans, etc on a dual core likely draw no more than 120-150W, so a good 650W should be safe. You can run it through a few psu calculators to be sure, but that is my 2c...
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