Trying to use 2 PSUs

ibpalle

ibpalle

ibpalle

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Joined
6 Jun 2006
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282
Location
Leeds
Hi all

Yet another crazy idea I am trying out.

I have a 500W Enermax PSU lying about - it has 2 6pin GFX power connectors so I thought I'd use that extra power supply to power one of the GFX cards in my triple SLI config.

I connected it, shorted the green and black wire to power it on and the fan came on fine. Then connected the 2 PCI power cables to my third GFX card and powered the system up. Booted fine, windows starts but as soon as I get into Windows - black screen.

Did some searches on the net and as far as I can tell - only thing needed is to short the green and black wires to power the PSU. I have done this a couple of times with the PSU in my build when I needed to bleed the watercooling loop (found a 12v power brick lying about so connected a molex and is using that now - very handy) and that worked fine.

I am assuming the PSU is not actually supplying power on the PCI connectors even though the PSU is powered on. I assume this because when I connected the 2 cables to separate cards the boot was fine, windows came up but as soon as I started Unigine, black screen again.

So what am I missing - any ideas?
 
IT depends on the PSU. I gleaned that some modern PSU's will check for load.

I was looking into this a while back and ended up buying a Thermaltake GPU PSU. I think it's a 250 Watt version. The fan on mine's a bit noisy, but they work fine otherwise... Worth looking on auction sites etc...
 
Hmm, yes it must be load checking - when I connected the PSU to 2 cards I heard clicking - possibly a contact activating and deactivating.

I do have another PC, my fileserver. Possibly I could route the gfx power from that - not using any gfx atm in that one so theres headroom. Just one thing - routing 2 6pin connectors over 2m! :)

Will have to sleep on it.
 
Higher specced power supply is of course the right thing to do - I was just playing with the option to see if MOAR power would allow me to drive the gfx cards higher than my current 1KW one instead of investing in a 1K+ PSU immediately. The 1KW one was expensive enough :)

I was trying this using an old Enermax 500w PSU. I just switched it for a 650 Corsair I had but the same problem occurred - both detect load somehow and turn off if they cant find any.

I tried using a molex rail to power fans and pump but that was not load enough - at least for the Enermax one - the power switched on and off with it connected to the peripherals too.

So the question is now to research how the load is detected and if I can cheat the PSU somehow :)
 
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