How to select which of the graphics cards to use

[dfsdfgfkjsefoiqzemnd]

I recently upgraded to a dual GTX770 setup, but my PSU turned out to be insufficient to feed both cards. Seeing as I won't be able to get a heavier PSU before next week, I have disabled SLI again and now the PC appears to be running only on the older card (GPU1). The other one remains idle no matter what I do.

Is there some way I can tell the PC to use the new one (GPU2) instead and let the old one idle? Furmark or Unigine don't appear to have options to test a specific GPU.

I'd like to bench the new card for a couple of hours to make sure it works, but am reluctant to open the PC yet again and swap the cards around.

I know, I'm being lazy.

I considered turning off the first card in Windows' Device Manager, but am a bit worried about side-effects like the benching card heating up the disabled one.

Sorry if this sounds like a noob question.

[SAV1OUR]

your graphics cards will always work based on the pci slot, so no. if your first 770 is in the top slot it will automatically use that one   

[theelitegamer]

your graphics cards will always work based on the pci slot, so no. if your first 770 is in the top slot it will automatically use that one   

What he said... what's ever on the top it sets that one as ''king''. I thought linus said there was a way... I'm not sure.. I'll look for a video for when I heard it. 

[mvitkun]

@Captain Chaos

sometimes there are options to disable pcie slots in the bios.

[dfsdfgfkjsefoiqzemnd]

Guess I'll open up the case again then. But not tonight, I'd like to use the PC for a change.

[dfsdfgfkjsefoiqzemnd]

Looks like I (more or less by accident) found a trick after all. Here's how I did it

1 ) Plug the monitor cable(s) in the 2nd card.

2 ) Boot the PC

3 ) open Device Manager -> display adapters, then disable the first card.

4 ) Let the screen flicker while the PC adjusts everything, then re-enable the first card again.

5 ) Open your benchmark and monitoring tools and run them.

I verified this during a 15-minute burn-in test with Furmark, during which I held one of my fan controller's temperature sensors against the heatpipes of both cards. It registered a much higher temperature on the bottom card's heatpipe than it did on the top card's.

-----

5 minutes into a Furmark 15 minute burn-in test :

GPU1 : 45°C according to furmark

heatpipe 1 : 43.0°C according to sensor

GPU2 : 80°C according to furmark

heatpipe 2 : 52.4°C according to sensor

Note the 2°C difference between GPU and heatpipe 1, and the 28.6°C difference on the 2nd card. The difference can be explained by the fact that hot air rises. When I measured heatpipe 1, card 2 was heating the first card completely and the sensor was also surrounded by the hot air coming off card 2.

I assume that when I reboot, it'll switch back to using the top card.

Doesn't matter, I am now pretty confident that the card should be fine. Time to fire up Dayz for some more testing.

EDIT : Turned the PC off, rebooted the next morning and ran Furmark again. It's still using the bottom card. I assume that it's because there are no displays attached to the top card.