Run 2nd GTX 480 on separate psu?

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CompuG##K

Gawd
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Jul 9, 2008
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So I've got a 2nd GTX 480 that will be coming soon and I haven't the power supply to run SLI quite yet. I do however have a PC P&C Silencer 610w laying around doing nothing at the moment. Is there any risk to using the paperclip method or perhaps this and powering the 2nd GTX 480 off the 610w psu until I can get a more permanent solution? I know this has probably been attempted before, but I just wanted some input before I go and do it.

Thanks.
 
What is your current power supply? Generally it isn't a good idea to have a second power supply unless you can sync the times they turn on and off. The modlight thing would work, but the paperclip is a bad idea.
 
Ive always been curious. I think there used to be a GPU dedicated psu 3.5 adapter.
 
Looks like that Modright thing would work. Its interesting. You can try it :) and report back.
 
My current unit is a Tagan BZ700 700w power supply. It is semi-modular and uses these coaxial screw on type modular cables. The unit came with a 6-pin and an 8-pin cable, but has ports for two of each. Even if it did have the two extra cables that are needed, there's no way I'm hooking up two 480's to a 700w power supply...

I might give that modright a shot. It's going to be several weeks before I can get the power supply I'm looking at and I'd like to see if I can get SLIPatch working correctly on my x48 board before then. I will be using the Antec HCP-1200 in my current build (sig below) as well as what I intend to upgrade to later in the year. I wanted to go big so I would have plenty of room to upgrade in the future.
 
That cable you linked is effectively the same thing as using the paperclip method, except it automates the process. Using it would work, but logistically, I think you're far better off simply buying a better PSU.
 
It would work fine if turned on/phased directly at power on. Make sure you use the same dogleg for external power as well. I do not recommend it, you are doubling failure factor along with possible user error.
 
what's wrong with using two power supplies and why is it bad to begin delivering power to the second GPU before the computer turns on (via paperclip)? has anyone tried this before?
 
serpretetsky said:
what's wrong with using two power supplies and why is it bad to begin delivering power to the second GPU before the computer turns on (via paperclip)?
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Nothing's wrong with using two PSUs, and I don't think anything bad would happen if the GPU is provided with power before the rest of the PC is turned on.
 
Crossloading isn't a problem for PSUs with independently regulated designs or for newer units that use DC-DC VRMs on the secondary to derive the minor rails from the +12V rail. Both of the OP's PSUs use independent regulation, so there shouldn't be an issue.
 
If anything this would be just a temporary solution until I am able to get a new power supply. I will definitely get the Modright cable instead of using the paperclip trick if I do attempt it. Thanks for the input guys.
 
Power supplies convert AC to DC. AC amplifiers are rated RMS and modern DC power supplies are rated with an 80+ standard. When converting AC to DC a drop in current happens, other components such as transformers and filters work the voltage down to what is needed, 12v, 5v etc...

When two PSUs are used instead of one you do not just get the added sum of wattage. Each one of those PS's have different characteristics , they are devices that need a certain amount of power to operate correctly. They will both draw a current from your wall socket and the rectifiers contained within will bias at a certain point in time on each of them. At this initial point of boot up is where uncharacteristic spikes in performance can occur, especially if a device (motherboard) is adding the load.

So you buy a pre-made secondary power supply, whats that doing? Common ground and COM ON are grounded together that parallels itself to the main PSU, exactly what you are talking about doing with a paperclip. The difference is the pre made device uses shielded connectors with good dielectrics and uses filters to offset any flux at post.

So don't use a paper clip, actually use some good wire with those tiny tyco ends you can get at radio shack (sometimes nowadays) and fix it up right. Turn it on and cross your fingers. If you used actual copper wire with proper ends and grounded the 2 PSU together you should be just fine.
 
Brilhasti said:
So you buy a pre-made secondary power supply, whats that doing? Common ground and COM ON are grounded together that parallels itself to the main PSU, exactly what you are talking about doing with a paperclip. The difference is the pre made device uses shielded connectors with good dielectrics and uses filters to offset any flux at post.
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What "flux"? When you use two PSUs in this way, they don't interact with each other at all. Each PSU is powering something different. It doesn't matter if you connect their grounds together since they already share a common ground.
Spooony said:
Why not just use the antec 1200w?
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Because he doesn't want to buy a new PSU. Why not just use your brain instead of making a useless reply to this thread?
 
Flux = circuits or crappy PSU without rectifier smoothing circuit built in. That reservoir cap can make a difference on initial startup "in this situation", even with common ground shared.

You are right, and like my last statement, just use decent wiring and parallel it and it should be fine.
 
Zero82z said:
What "flux"? When you use two PSUs in this way, they don't interact with each other at all. Each PSU is powering something different. It doesn't matter if you connect their grounds together since they already share a common ground.

Because he doesn't want to buy a new PSU. Why not just use your brain instead of making a useless reply to this thread?
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Actually, I do want to buy a new PSU, but it will be quite some time before I will be able to. In the meantime, I'd like to test my second GTX 480 in SLI and see if I can get SLIPatch to work on my x48 motherboard. That's where the 2nd psu comes in. If I can't get SLI to work on this board, no big deal. I plan to migrate my 480 SLI setup (and Antec HCP-1200 I'm eventually buying) to a new build later this year.
 
Brilhasti said:
Flux = circuits or crappy PSU without rectifier smoothing circuit built in. That reservoir cap can make a difference on initial startup "in this situation", even with common ground shared.

You are right, and like my last statement, just use decent wiring and parallel it and it should be fine.
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You're aware that all decent PSUs have quite a bit of filtering, right? It doesn't matter what kind of wiring you use. Connecting the PS_ON and ground wires of two different PSUs together isn't going to make any difference to the performance characteristics of either PSU.
 
Zero82z said:
You're aware that all decent PSUs have quite a bit of filtering, right? It doesn't matter what kind of wiring you use. Connecting the PS_ON and ground wires of two different PSUs together isn't going to make any difference to the performance characteristics of either PSU.
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Yeah I am, and you are correct. Im just an old school analog guy! lol

But hey, it could go wrong... lol

And as far as kind of wiring does not matter I do disagree on that point. A paper clip can lead to problems.
 
Well, if we were dealing with really simple and low-end PSUs then that would be valid, but those kinds of units would also not be safe to use with a computer in the first place.
 
The best solution is to get a better psuthat can hold the load of 2 480GTX..

$700 worth of hardwares (2X 480) need a decent power supply
 
For the short term, I have used an Antec 450w power supply using the paperclip method to power a 6850 card with the rest of my computer being powered by a 500w. I did what everyone has mentioned, powered the card on a second before pushing the power button on the computer. No problems at all for the month that i had to use the ghetto rigging.
 
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