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Two psu on one graphics card

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  • Power Supplies
  • Computers
  • Graphics Cards
  • Graphics
Last response: in Graphics & Displays
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August 7, 2014 8:16:13 PM

So I am currently building a computer that has two power supplies (400W and 350W) since I dont have the money to buy a new one.
My graphics card requires two 6pin pcie connectors but both of my power supplies only have one each.

So my question is, will it be okay for me to use one 6 pin pcie connector from each psu as long as I equally distribute the rest of the parts to each psu?

My other option is to get an adaptor from molex to 6 pin pcie but I would rather not spend money if it is not necessary.

The graphics card is a evga GTX560ti.

More about : psu graphics card

a b ) Power supply
a c 428 U Graphics card
August 7, 2014 8:35:27 PM

I would highly recommend doing neither. The molex adapter isnt the best option, but its the better of the two.
I would personally save up for a new power supply.
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Best solution

a b ) Power supply
a b U Graphics card
August 7, 2014 8:36:51 PM

Putting a "Frankenstein PSU" together that way is not likely to work well since the PSUs lack proper load-sharing circuitry. You will either end up with the PSU having the stronger 12V rail taking all the 12V load or the PSUs going into oscillation if the PSUs start "chasing" each other: the stronger PSU's output voltage rises, takes load off the weaker PSU, the stronger PSU's output voltage starts sagging, the weaker PSU starts picking up load again, rinse and repeat.

Depending on your luck, the results may not be pretty... instead of needing a proper PSU for $50-70, you may end up blowing up all your components including both PSUs and needing a whole new PC instead including a proper PSU you should have bought in the first place.
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a c 122 ) Power supply
a c 250 U Graphics card
August 7, 2014 8:48:46 PM

I hope they're both good quality - from tiers 1, 2a or 2b of http://www.tomshardware.com/answers/id-1804779/power-su...

You're going to find that from moment to moment the connectors aren't giving out the exact same voltage with 2 psu's - especially 2 with large variations in voltage. This isn't going to prolong component life. If the variations are large enough it'll show up as eg frame stuttering, pixelization, overheating, poor performance, etc.
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August 7, 2014 9:04:46 PM

Does the Lian Li dual psu adapter not regulate the load on each psu properly? I thought if I used one psu on my graphics card and the other on everything else it would be okay..

Thanks for the opinions though! I'll look into other psu's and try to buy one later then and put this project on hold.
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a c 122 ) Power supply
a c 250 U Graphics card
August 7, 2014 9:09:46 PM

Never heard of the Lian Li dual psu adapter - you'll have to look into specs.

Lian Li are usually expensive cases. Which model have you got?
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a c 122 ) Power supply
a c 250 U Graphics card
August 7, 2014 9:35:23 PM

Ok - so you just get constant electrical shorts with variation in voltage from one to the other And that's just for the motherboard. What about the graphics card?
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August 7, 2014 9:54:20 PM

i7Baby said:
Ok - so you just get constant electrical shorts with variation in voltage from one to the other And that's just for the motherboard. What about the graphics card?


I have a evga GTX560ti
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a c 122 ) Power supply
a c 250 U Graphics card
August 7, 2014 10:57:12 PM

It has two 6 pin connectors. Are you going to use one from each power supply?
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a b ) Power supply
a b U Graphics card
August 8, 2014 3:50:40 AM

i7Baby said:
It has two 6 pin connectors. Are you going to use one from each power supply?

That is exactly what OP's first post says... GPU + "equally distribute the rest."
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a c 122 ) Power supply
a c 250 U Graphics card
August 8, 2014 3:58:24 AM

Let him answer
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a b ) Power supply
a c 78 U Graphics card
August 8, 2014 4:07:17 AM

Should work, but you will probably need to wire in the power switch to the secondary psu so it powers up.
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a c 122 ) Power supply
a c 250 U Graphics card
August 8, 2014 4:29:15 AM

I'd never recommend using two poor quality power supplies in unison to run a pc. You're just asking for trouble.
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a b ) Power supply
a c 78 U Graphics card
August 8, 2014 4:51:06 AM

I agree, I wouldnt recommend it either, but it should work (which was the question).
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a b ) Power supply
a b U Graphics card
August 8, 2014 5:07:08 AM

RobCrezz said:
I agree, I wouldnt recommend it either, but it should work (which was the question).

That is a very hypothetical "should."

Best case, whichever PSU has the highest output voltage will take most of the load since the other PSU will not be providing any power until wiring losses bring the "stronger PSU" outputs down to the "weaker" PSU's level, which is not going to be anywhere near even between the two PSUs unless they are almost perfectly matched..

Worst case, the two PSUs will bounce load between each other, go into oscillation or some otherwise unstable operating mode - assuming the PSUs even needed any external "help" with that, destroy each other and possibly take the rest of the computer with them.
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August 8, 2014 7:47:54 AM

i7Baby said:
It has two 6 pin connectors. Are you going to use one from each power supply?


Yeah my main question was whether or not using one from each power supply was a bad idea. Then my other solution was to get an adapter for a molex to 6 pin so that only one psu was powering my graphics card. But from the looks of it, most of yall agree that I should avoid that and just get a new psu haha
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a b ) Power supply
a b U Graphics card
August 8, 2014 7:53:10 AM

Johnnam93 said:
But from the looks of it, most of yall agree that I should avoid that and just get a new psu haha

There are just too many ways this could potentially go wrong.

It MIGHT work... it would probably work at least somewhat. But if it does not, you could lose everything.

Not worth the risk.
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