I'm a little confused. First my machine:

Themaltake SPEDO case
i7-950 processor, FOUR cores (NO hyperthreading)
Win 7 Professional
ASROCK x58 Deluxe MB (newest BIOS)
12GB GSKILL Trident memory
Silverstone ST1500 PS
nVidia 196.21 drivers

My unit will recognize and utilize any combination of up to FOUR video cards that I install.... NO SLI. But, the Silverstone 1500-watt PS will only handle up to TWO GTX-295's, four cores running independently at full bore, per Silverstone's.... GPU Suppport List

I know this is true because I had two GTX-295's, one GTX-275 and one GTX-260 all running SETI@home full-bore no SLI, all six cores humming out work units, and after about one month PIN-10 of the 24-pin MB connector melted, messing up the PS and the MB. I had to replace both, and that was expensive.

Yesterday, I installed a second PS in the bottom front of my Thermaltake SPEDO case, 1200-watts, which should handle an addtional two GTX-295's. I jumpered between the green and black pins on the MB end of the 24-pin cable on the second PS, to make that PS stay on while it is plugged in.

It ran excellently on SETI@home with FOUR GTX-295's, all eight CUDA cores pumping out work units.... for about 45-minutes.

Then the second PS suddenly went off and will not come back on. Something inside of it died, but there was no unusual sound or any odor. Which I suspicion relates to a power problem on the outlets in my office area, not enough juice to feed a 1500-watt PS and a 1200-watt PS from that one line. I need to run another outlet from the breaker box to feed the second 1200-watt PS.

My point being, that with dummy plugs installed on the second, third and fourth video cards, and the right settings in nVidia control panel... and the right MB... WIN 7 recognizes and handles up to eight cores of four video cards. Just don't try running all of them at full-bore for very long... not even on a 1500-watt PS.

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I DONATE money to SETI@home.... DO YOU?

I'm just slowly BOINC'ing along.

Hey... ET... you have a sister who likes earthlings?

That will be very usefull information. I can see my build possibly requiring multiple power supplies before I am done, and I was concerned about getting 2 GTX 480's working under Win 7.

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Warning, addicted to SETI crunching!
Crunching as a member of GPU Users Group.
GPUUG Website

Ouch. An expensive lesson.

You are correct. Although I'm no electrician I've done a little wiring to the Ontario building code in an addition I built. The **entire** circuit on which all the plugs, light switches, etc. reside running back to the main panel **must not** exceed 80% of 1800 watts (on the normal household 120 volt line) to be within code.

Essentially: 15 amps (your usual household current) X 120 volts * 80% = 1440 (or say a 1500 watt heater at max).

Plugging in two PS's into the same circuit that can ramp up to 1500 plus 1200 watts (beyond what other load might also be on the line) would undoubtedly risk overloading it (see MSATTLER's recent posts on those kinds of adventures). All the electrical devices on the line would suffer as a result, once they collectively started topping out.

I have a new cruncher I have a watt meter running on just to keep an eye on it and I'm pushing 700+ watts presently at full-bore. I'm already thinking about where it will ultimately reside and whether I have to consider it on its own circuit to protect the investment.

Normally you will pop a breaker before doing too much damage (especially in regards to heating up the wires running with in the walls for instance). That you didn't says either you might have plugged the one PS into a different circuit than the second (to my surprise I discovered once that I actually have a number of plugs in the cottage that deliver two full separate independent circuits!).

More likely you have a problem back at the panel where it is not tripping the breakers (or blowing the fuse) before damage is done. "Damage" is well described in MSATTLER's posts where he narrates what sounds to be nearly a close encounter with a house fire.

Regards,

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