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Power Adapter Help for Graphics Card

Last response: in Graphics & Displays
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November 30, 2011 9:28:50 PM

Hi, I couldn't decide if this belonged in the graphics or PSU section. So anyways, I just picked up 2 XFX 8800GTX's for cheap to put in sli. I noticed that they each take 2 6 pin PCI-e power connectors for a total of 4. My power supply only has 2 6-pins. I have an adapter for a 12V Molex to 6-pin, will that work if I use that plus buy an another? Or do I need two of the adapters that each take 2 12V Molex? Hopefully that all made sense. Hope to hear back soon from the Tom's community :) 

EDIT: I also have an EZ Plug on my mobo, can that help with power any?

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a b U Graphics card
November 30, 2011 9:50:39 PM

I'd go with two of the 2-molex adapters to be safe. I don't know if one molex can deliver enough power for a 6-pin PCI plug.
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a c 153 U Graphics card
November 30, 2011 9:52:33 PM

Yes the EZ Plug can help, for ease of mind if anything.

What powersupply do you ahve first off. Are we sure it can power two 8800 GTXs?

Lol, pizza man, awesome name.
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November 30, 2011 9:55:31 PM

Alright, thank you. I suspected as much. Gonna buy a set of two PCI-E 6-pin to 2 molex adapters. Only $4 w/ free shipping :) 
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November 30, 2011 9:56:35 PM

Helltech, I have a 600w Enermax Noisetaker. According to the PSU calc I should have plenty of power to spare.
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a c 153 U Graphics card
November 30, 2011 10:02:13 PM

From what i found you need 462w of power at peak.



http://www.silentpcreview.com/article221-page3.html

According to that review your power supply isn't rated at 80 percent efficient, so lets say its 75 percent efficient (the review says 71-77). Thats 450w of power. Now I'm not going to bust you up too bad and say it wont work at all. But realistically speaking it might not, and I doubt it will. Just be prepared that you might have to buy a new PSU.
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a b U Graphics card
November 30, 2011 10:47:34 PM

You've got it the wrong way. The PSU's 75% efficiency means that it should supply 600W safely, and the 600W will be 75% of the power that it draws from the wall. It will use 800W total, but the cards will be fine.
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November 30, 2011 10:59:40 PM

Alright well, I don't particularity want to spend the dough for a new PSU, the cards were gonna be the last upgrade for this system. It's a 939 Socket and only takes DDR. If for some reason there's not enough power how will I know? No boot? Underclock at boot? Or just poor performance? My power supply is pretty old. Like 3-4 yrs old I believe. Should I be worried about it failing anytime soon? When the system is powered down there's a slight buzzing from the PSU, but I think that is because it's plugged into a power strip. What worries me though is I can no longer overclock my HD4830 that's currently in the system, not even by 1Mhz. Could this be caused by the PSU or a failing card?

P.S. Sorry to change the subject in the same thread
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a b U Graphics card
November 30, 2011 11:03:40 PM

A shortage of power shouldn't stop you from booting unless the PSU really goes bad, as the GPUs aren't under load during the boot process. If you've got a working PSU that doesn't supply enough power, you'll probably see crashes, usually in-game. Underclocking happens because of overheating, not underpowering.
Could you describe the buzzing further? Coil whine is a fairly common phenomenon (I've got it), but it should usually happen under load.
If the PSU really fails, you'll crash all the time, and will fail to boot.
That GPU issue is due to the card itself or caused by a software problem.
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a c 153 U Graphics card
November 30, 2011 11:04:45 PM

Well I had a 500w PSU that (still works fine to this day mind you) couldn't power a single GTX 260. The system would boot up, but never post. However a Corsair 450w worked fine. So yeah...
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December 1, 2011 6:21:18 PM

Thanks kajabla, I'm relieved to hear my GPU problem isn't the PSU. The sound is a very soft kind of high pitched (basically just not low pitched) buzz. I have to be pretty close to hear it, and if I flip the switch on the PSU to off it sounds like it winds down then stops. I'm prolly just bein paranoid, from what I've read it's likely the fact I have it plugged into a power strip with some other things plugged in.

Thank you Helltech and kajabla, I appreciate the input you have provided, and I learned some new things too!
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a b U Graphics card
December 1, 2011 11:37:46 PM

Try it on a wall socket. I'm betting it'll continue. Sounds coil-whine-ish: you're safe.
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December 2, 2011 3:58:39 AM

Best answer selected by PIZZA Man.
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December 2, 2011 3:59:38 AM

Alrighty, will do. Thank you kindly for all your help :) 
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