I am considering upgrading to a dual-gpu setup (460's or 570's), but am uncertain if/which of my current PSU(s) can safely handle the extra load for 24/7 unattended crunching.

Currently I have an AMD 6 core 1090T mildly OC'd 3.7ghz
Asus M4A89GTD PRO/USB3 (2 PCIE @x8)
HD - 1 boot SSD, 3 SATA, 1 PATA DVD
Cooling: excellent roomy ancient modified CPPC 10-bay case; Fans: 2x80mm intake, 120mm and 140mm exhaust, 2x80mm internal

Scythe SPSN-070 "Stronger" 700w PSU with 4x PCIE 6+2 pwr cables "SLI/Crossfire ready". ATX 2.3, 80plus, promising 170w/24A 3.3v and 30A 5v. 530w/47A on the 12v1 line 25A 12v2 line,

Owltech PSGCM700 700w PSU with 2 PCIE 6 and 1 PCIE 6+2 cables, SLI-ready, ATX 2.2, 80plus, promising 155w for 36A 3.3v and 30A 5v, and 675w/18A 12v1,2,3,4 each line.

Should I feel comfortable using either PSU for a dual GTX460, or possibly dual 570 setup? which would be the better choice? If both PSU's are inadequate for dual 570's (even dual 580's), what PSU would be adequate? I know raw PSU wattage alone varies by quality/maker, so thoughts on the differing power distribution characteristics when selecting for multiple GPU's? who knows, perhaps some 4-GTX460 mobo is in my future. Thanks, and Merry Xmas!

Well the 2 x GTX460 would pull 320w (in theory) and run cooler. Performance isn't great though as the GPUgrid app basically only utilizes 2/3rds of the 336 available cores.

For 2 x GTX570 you'd be pulling 438w (in theory). They run much hotter. Performace is much better though and all 480 cuda cores are usable.

Add the power of the other components (CPU, HDD's and SSD and some more for the motherboard) and you'll have a better idea of power supply required then add 20% on top as good power supplies are only 80% to 90% efficent (the cheap ones are worse). I'd probably put a 850w PSU if you wanted a dual GTX570 setup.

From the running cost point of view the 570 is going to generate more heat and eat electric, so maybe start with a single GTX570, say one of the OC'ed versions and you'll be pushing the wu out pretty quick.

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BOINC blog

Well the 2 x GTX460 would pull 320w (in theory) and run cooler. Performance isn't great though as the GPUgrid app basically only utilizes 2/3rds of the 336 available cores.

I was hoping this would have been addressed by now. Guess not. Not a problem on other projects though.

I'm only running 850 Watt PSU's on my 3 Dual GTX 580's and 750 Watt PSU's on my Dual GTX 570's. One or 2 of my GTX 570 Box's may even have 650 Watt PSU's in them, I didn't bother to take them out so I could read what they were when I put the 570's in. They ran so I was good to go but I know some of those Box's have only 650 Watt PSU's in them ...

I'm only running 850 Watt PSU's on my 3 Dual GTX 580's and 750 Watt PSU's on my Dual GTX 570's. One or 2 of my GTX 570 Box's may even have 650 Watt PSU's in them, I didn't bother to take them out so I could read what they were when I put the 570's in. They ran so I was good to go but I know some of those Box's have only 650 Watt PSU's in them.

They were running Dual HD5870's so I didn't see why they wouldn't run at least Dual 570's. I didn't want to take the chance on the 580's so I put new 850 PSU's in those Box's ...

The 1090T is a 125w TDP part
Disk drives about 7w at worst x4=28w
Motherboard with controllers 8gb mem ?? 30w ??
6x fans ?? 1w each, for 6w ??
(do these ??guesses?? seem reasonable for memory and fans?)

For system total of about 180w, + video (GTX460@160w per, GTX570@219w per).

Dual GTX460 (adding a second) =320+185=500w /.8 = 632w worst case... doable, even mild overclocking and 100% CPU utilization.

Dual GTX570 (buying 2) 420+185=605w /.8 = 756.25w yeesh. (Risking flaming meltdowns taking out 5 neighbors houses in one go because they are only 1 meter away in Japan would leave me financially liable. Not worth it for just a DC hobby)

Rather than invest in a more inefficient 224 Cuda core GTX460 for the psychic benefit of dual GPU's never to run in SLI, I think adding 960 Cuda cores with two GTX570's and rejiggering my cards around to available motherboards makes more sense at this point in terms of shaders/$$/watt. Single GTX570's could go into my two 700w PSU AMD boxes at home, the current GTX460 goes to my daughter, and her 9800GTX+ and 9800GT goes into my wife's Core2Duo box with dual PCIE slots. I will need to check both of those PSU's for suitability, but assuming I initially overbought as usual and they don't need replacing it should work out fine. If a replacement PSU is necessary then an 850w or better would be a reasonable choice allowing dual GTX570's or even a GTX580(s) in the future, and moving PSU's and video cards downstream.

Two questions left:
-can/should a mismatched Fermi pair (460 & 570) peacefully coexist in a single W7x64 box?
-Desireable GPU PSU power distribution, i.e. the Owltech's even 18A per 12v lines 1,2,3,4, or the Scythe's 12v line 1@47A and 12v line 2@25A ?

Thanks for the expert guidance, and Merry Xmas once again.

Two questions left:
-can/should a mismatched Fermi pair (460 & 570) peacefully coexist in a single W7x64 box?

I have a GTX 580 and a GTX 480 in the same PC, and they work just fine, though there is no official NVidia driver supporting both cards (I'm using the GTX580's). Your case would be similar, so I guess a 460 & 570 would work together.

-Desireable GPU PSU power distribution, i.e. the Owltech's even 18A per 12v lines 1,2,3,4, or the Scythe's 12v line 1@47A and 12v line 2@25A ?

My other PC with two GTX 480s (overclocked to 780MHz and 800MHz) draws 713W from the 230V AC line at maximum GPUGRID utilization (running two KASHIF_HIVPR WUs at the same time with a C2Q 9650 CPU @4GHz), using a Chieftec 80+ APS135-1000C PSU. I would prefer Owltech's 700W PSU, because a PSU with many lower powered 12V rails is much safer (but they have to meet the GPU's power requirements) than a PSU with a higher powered 12V rail. Read more here, here and here (see myth 3).

-Desireable GPU PSU power distribution, i.e. the Owltech's even 18A per 12v lines 1,2,3,4, or the Scythe's 12v line 1@47A and 12v line 2@25A ?

I would prefer Owltech's 700W PSU, because a PSU with many lower powered 12V rails is much safer (but they have to meet the GPU's power requirements) than a PSU with a higher powered 12V rail. Read more here, here and here (see myth 3).

Thank you for the links; useful information for a higher-performance PSU initiate.

Basics such as 12V x 18A = 216W for the 6-pin connector of a 570 and 12V x 20A = 240W for the 6+2 8pin connectors for the 480 and 580's TDP figures make more sense, and the PCIE connector itself providing up to 75W (12V @6.25W) power for the card via the ATX connector.

Years ago a flaky dual-Xeon S2DGE required a train and suitcase travel up to Tokyo's Akihabara tech support to learn an inadequate PSU was the cause, and an early Tyan Tiger MP dual-AMD setup that melted an ATX connector has made me more power-user wary. Forewarned is forearmed, and multiple high-performance GPU's is virgin territory for me (Pioneers, I salute! you ;p ).

In the end it seems both 700w PSU's are more than adequate for single GPU use, but not up to multiple top-end GPU needs, so my next PSU will be +850w with all the right connections.

Zombie67 had a performance issue with his GTX580. The card completed tasks slower than it should. The problem was caused by an inadequate PSU which required connecting Molex power connectors into a Y concentrator to feed the 8pin power input on the GPU. This was insufficient due to the limitations on the PSU rails and did not supply enough power. On replacing the PSU with an 8pin GPU power connector the system worked as required. The tasks probably completed slower because the GPU was reducing the frequencies of the card. The use of Molex converters is generally unadvisable for GPU’s.

From this thread,
http://www.gpugrid.net/forum_thread.php?id=2327