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SFX Power Supply with 2x8 pin GPU

post #1 of 8
Thread Starter 
Hey guys! So I'm planning a Compact Splash build. I'll be using a GTX 780 HOF, which uses two 8-pin PCI power connectors.

This seems like it could be a bit of a problem with the SFX power supply (the Silverstone ST45SF-G) that fits in this case. It only has a 6-pin and an 8-pin PCI cable.

How could I go about using this GPU with this power supply? The only thing I could think of was to use an 8-pin for one, and then use a SATA power to 8-pin adapter for the other one. Is using an adapter like that a bad idea? How else could I make this work besides waiting for an SFX form factor PSU that supports dual 8-pin PCI?
post #2 of 8
Quote:
Originally Posted by Heuristic View Post

Hey guys! So I'm planning a Compact Splash build. I'll be using a GTX 780 HOF, which uses two 8-pin PCI power connectors.

This seems like it could be a bit of a problem with the SFX power supply (the Silverstone ST45SF-G) that fits in this case. It only has a 6-pin and an 8-pin PCI cable.

How could I go about using this GPU with this power supply? The only thing I could think of was to use an 8-pin for one, and then use a SATA power to 8-pin adapter for the other one. Is using an adapter like that a bad idea? How else could I make this work besides waiting for an SFX form factor PSU that supports dual 8-pin PCI?

it isnt a bad idea, just make sure the PSU can handle the whole system.
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Orange Angel
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BOINC me! (TM)
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post #3 of 8
Thread Starter 
Quote:
Originally Posted by PCSarge View Post

it isnt a bad idea, just make sure the PSU can handle the whole system.

At full load, Hardocp measured my card as drawing 422 W at the wall. I believe that was the whole system at the wall.

Is this acceptable for a 450 W PSU, or pushing it?
post #4 of 8
That 450w psu will be near it's limits. I'm currently pulling 520w at the wall with an 80plus Bronze 600w Silverstone. That's around 415w at the PSU. This is with a 780 classified at 1.35v and a 3570k. Full load on both.

Assuming you'll be using the hardware in your sig..... You can't overclock the cpu and depending on the gpu overclock the PSU should be alright.

Measured with a Killawatt
 
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post #5 of 8
Thread Starter 
Quote:
Originally Posted by G3RG View Post

That 450w psu will be near it's limits. I'm currently pulling 520w at the wall with an 80plus Bronze 600w Silverstone. That's around 415w at the PSU. This is with a 780 classified at 1.35v and a 3570k. Full load on both.

So, essentially, what matters for the rated power output of the PSU is not what you measure at the wall, but what's actually delivered to the components? So I could draw ~450 at the wall and I wouldn't actually be at the 100% limit of the PSU?

I won't be running my GPU over 1.2v so my power load should be quite a bit less than yours.
post #6 of 8
Quote:
Originally Posted by Heuristic View Post

So, essentially, what matters for the rated power output of the PSU is not what you measure at the wall, but what's actually delivered to the components? So I could draw ~450 at the wall and I wouldn't actually be at the 100% limit of the PSU?

I won't be running my GPU over 1.2v so my power load should be quite a bit less than yours.

The power rating is at the unit, before the ~20% inefficiency.

That unit is a single rail with 37amps, it should be fine for a 1.2v 780 and a locked quad core.
 
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post #7 of 8
Thread Starter 
Thanks for your help.

One more question. I'm thinking of creating a custom cable (since I'll be custom sleeving new cables for everything anyway). I'm considering making a cable with a SATA connector passthrough in the middle, and then the 8-pin PCI cable that I'm missing on the end.

The PSU, which is modular, has 2 free 6-pin slots to plug cables into. If I were to combine these two into the singular custom cable I'm making, would that cause any problems? If you're having trouble visualizing, I would take two +12V from one modular output, one +12V from the other, and then take any ground wires I need from both of them as I need them. (I'll need 5 ground wires for the 8-pin PCI connector, and the modular outputs provide 3 each.)

I'm not sure if this creates a parallel circuit or not, which would be pretty bad I think. Is combining modular outputs into a single cable unheard of? My thinking is that since it's a single-rail PSU, all the +12V are going to the same place in the end, so it wouldn't be parallel. And of course all the grounds are ground.
Edited by Heuristic - 11/13/13 at 7:34am
post #8 of 8
The one in question is a formidable psu to say the least, but even if you used the converters, I doubt if the psu could handle that load and the rest of the system too. look at some reviews, switch case, or see if there is a way to get a ps2 psu in it. Worst comes to worst, you can always go with a weaker card. thumb.gif
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