i have been using an ASUS GTX670 DC2 Top for about 9 months now, and recently decided to get another one of those to try out a SLI setup. However, the Top version of that card is sold out, but as it is simply an overclocked version of the normal DC2 and I had read of people running them in SLI, I ordered a normal DC2.
Today, the new GPU arrived, I put it into the system, connected all the power cables and the SLI bridge and booted the system. Everything was fine, and after Windows did it's driver thingy, I could select SLI in the NVidia Control Panel.
After this, I started first Skyrim, and then GW2 and monitored both cards stats with GPU-Z. Everything looked fine (temps were at around 65 degrees celsius, clocks were at their normal (different) speeds).
Then, after about 20 minutes in GW2, my PC shut down, and rebooted. Immediately, the fan of the new GPU went to 100%. In Windows, I couldn't select SLI anymore, and AIDA64 reported the PCI-E slot in which the card was to be empty.
So I shut down the PC, removed my old card, moved the new one to the primary PCI-E slot, and booted, but this time I didn't get any video output, and the fan was still at 100%. I read about people having issues because of too little power, or faulty PCI slots or power cables, but I tried all different PCI-E slots, different power cables, and my PSU is a Coolermaster Silent Pro Hybrid 850W, so I shouldn't have any power issues.
I also checked the card for any damages, broken capacitors etc, but everything looks just fine, and identical to my old card.
So, considering my PC is running just fine with my old card, my conclusion is, that the new card is faulty, and I should RMA it, but I'd like to hear your thoughts on this before I do it.
Sounds like a dead card... Before you RMA it, you can usually return/exchange the card with the store that you purchased it from. This is much less of a hassle than RMA'ing, especially given Asus's RMA reputation...
Since the card is NEW, I wouldn't probe much to figure out what's wrong with it, and if you do, stay within what you can do without voiding the warranty. The RMA department can use any excuse of damage or modification to deny you a claim.
If one card works, and one doesn't (no output etc.) then that card is defective. If BOTH cards work separately then it appears to be a software issue.
**He appears to have described EXACTLY THIS SCENARIO, so I can't fathom it NOT being a defective card. A potential SLI/driver issue makes no sense at all if one card works by itself and another does not by itself. That's obviously a defective card.