Amp requirment for the 580? Maybe I'm starving mine?

[Defoler]

Got a simple question.

I got an enermax 1250w psu, with 30A per 12V rail.
Also got a 1050w psu, with same 30A per 12v rail.
Each card is on its own rail.

The 1250 powers the CPU and 2xGPUs.
The 1050 powers all the pumps/HDDs/Fans and 2xGPUs.

So far so good.

Now, does the 30A per rail hinders the option to reach the card's requirments?

Before, I had 3 cards being powered by the 1250w PSU. Until I changed that, the system would halt when I tried to increase to OC up to a certain point. It would not shut down, just halt.
After I moved one of the cards to the 1050W PSU, I was able to push foward with OCing.

Now I got the same. Once I go over 968 core speed, the system halts in the same way. No drivers errors, just halt.

So is it the PSU? just not enough volts the on the cards?

What I can do, is use another rail and try to "split" it between two cards on each PSU.
Like card1 is rail 3+4, card2 is rail 5+4 (where 3 and 5 are the 8 pin connectors and 4 is the 6 pins).
Will this help?

I'm considering getting a couple of quattro 1200, which has a 38A per rail, but as I did some sleeving on my PSU, I'm going to lose some good money selling them.

[dengyong]

The 1250 would also be powering all the pci-e slots through the board.

[Defoler]

The 1250 would also be powering all the pci-e slots through the board.

Yes, but its currently on a different rail.
To be more specific:

PSU1 (6 rails 30A each):
1+2 - CPU+motherboard
3 - 580
4 - 580
5 - PCIE connectors+2 SSDs
6 - empty

PSU2 (6 rails 30A each):
1-2 - empty
3 - 580
4 - Pumps, Fans, 3 HDDs
5 - 580
6 - empty

But again, question is, are the 580s being staved by the 30A rails (GPUs at 1.213v)

[CraptacularOne]

You are lacking some very basic understanding of how your PSU works. Neither of your PSU's have 6 rails that can supply 30 amp at once. They have 6 rails that can supply "up to 30 amps" but not all at once. 6 30 amp rails would be 2,160 watts on the 12v. And that's about double what either PSU is capable of. Neither PSU is even remotely capable of delivering 180 amps which is what 6 30 amp rails would require if all loaded to capacity. 6 x 30 = 180. Neither PSU is even remotely capable of delivering that much amperage on the 12v rail. Now I'll just make this short for you by saying that even if either PSU was capable of putting it's total output over the 12v rail it would not come near 180 amps. For instance the 1250w unit if it could do this would only make just over 104 amps, while the 1050w unit would deliver 87.5 amps. That's assuming they could put their total combined wattage out over the 12v rail. Neither can do this. Now lets move on to the cards themselves. Even given the above information, I doubt you are "starving" your cards of voltage. If you were, the cards wouldn't merely stop as you say, the whole system would restart. What you are describing sounds like either your cards are just at the limits of what they can do on the given voltage 1.213v or your cooling limited.

[Frag Maniac]

According to EVGA (and MSI's chart), the 580 runs on the exact same amount of power a 480 does, 600w and 42 amps.

You are lacking some very basic understanding of how your PSU works. Neither of your PSU's have 6 rails that can supply 30 amp at once. They have 6 rails that can supply "up to 30 amps" but not all at once.

Yes it's combined, not individual, but the way you said it is a bit deceiving. The "Up to 30 amps" part I mean. The Revo 1250 actually supports up to 104 amps maximum all rails combined.

Here's a handy chart showing maximum combined 12v amperage on most PSUs: http://forums.guru3d.com/showthread.php?t=205763

The reason some prefer single rail designs instead Defoler is the PSU doesn't have to rely on fast switching MOSFETS to distribute the load. It's just a simpler design with less margin for error and heat. Not all MOSFETS are created equal, nor are all given equal heatsinks. In a good PSU multi rail is not an issue, but still, one could argue there is more that can go wrong in a multi rail design.

To answer your question though, I've yet to see any actual bench proof of how many amps 4 580s draw simultaneously, but if I were planning something like that, which I wouldn't, I'd want the very best PSU. I'd have gone with something like the Antec HCP1200. It's ability to sustain ultra high loads is beyond reproach from what I've read.

I would be careful how you go about your quad SLI 580 use. I'd stay away from folding or long sessions on high load games. Personally I can't see more than dual 580 being practical or needed. The extra FPS you get are just not usable at all.

[CraptacularOne]

@ Frag Maniac, no a GTX580 doesn't require anywhere near 600w and 42 amp by itself. That suggestion is for a whole system with a GTX580. A GTX580 draws about 244w which equals just over 20 amps. And that is only peak load not sustained, generally the usage is about 200w in a typical situation.

And the example given was just that. Read it again, I'm giving theoretical amounts based in the PSU's output as an example.

[darckhart]

yes, nvidia rates gtx580 at 244W (or about 21A) peak, and i'm not sure when OCP kicks in for the card, but assuming it has the 3 power sources (slot+6+8) makes it capable of 300W (or about 25A). taking your oc into account, and ocp of your psu +12V rails doesn't kick in until about 35A, i would assume that your cards are being fed more than enough juice.

[Frag Maniac]

@ Frag Maniac, no a GTX580 doesn't require anywhere near 600w and 42 amp by itself. That suggestion is for a whole system with a GTX580. A GTX580 draws about 244w which equals just over 20 amps. And that is only peak load not sustained, generally the usage is about 200w in a typical situation.

And the example given was just that. Read it again, I'm giving theoretical amounts based in the PSU's output as an example.

Yeah I didn't mean that was power the GPU only draws. EVGA, MSI and Nvidia always list it conservatively, meaning they mention the amount of power recommended for the whole system if that's the card you're using, which is the way I feel they SHOULD list it. Otherwise you'd have people on a budget that try to get the best system they can for the money thinking you only need a 300-400w PSU for a 480/580.

They also use conservative ratings because the efficiency and output while under great load varies greatly from PSU to PSU. In PSUs it's always best to allow for a bit of overhead and get the best unit you can afford for the hardware you're running.

I stand by what I said, I would not run four 580s on a mere Revo 1250. I've read stories of even two 480s stressing an HX1000 depending on the clocks and usage.

[CraptacularOne]

Yeah I didn't mean that was power the GPU only draws. EVGA, MSI and Nvidia always list it conservatively, meaning they mention the amount of power recommended for the whole system if that's the card you're using, which is the way I feel they SHOULD list it. Otherwise you'd have people on a budget that try to get the best system they can for the money thinking you only need a 300-400w PSU for a 480/580.

They also use conservative ratings because the efficiency and output while under great load varies greatly from PSU to PSU. In PSUs it's always best to allow for a bit of overhead and get the best unit you can afford for the hardware you're running.

I stand by what I said, I would not run four 580s on a mere Revo 1250. I've read stories of even two 480s stressing an HX1000 depending on the clocks and usage.

With a quality unit efficiency and output do not vary much at all under load. I'm by no means suggesting someone run a GTX580 on a 400w PSU. The Revo 1250 is a superb PSU.

Have a read about it:
http://www.jonnyguru.com/modules.php...Story&reid=145

It would easily be able to power a system with 4 GTX580's by itself. Especially when you consider that 3 GTX580's in an overclocked system draws just under 740w at peak load, adding a 4th GTX580 would be easy and well within the unit's capacity.

http://www.guru3d.com/article/geforc...-sli-review/14