Dual graphics card woes: Only one recognized

[_cp]

I have already troubleshot this to death, so I thought I'd see if anyone could help me out.

I have a 3 monitor setup and until recently have been using the following hardware:

Proc: i7 860
Mobo: Intel DP55KG
Ram: 16 gigs G.skill
Primary Graphics: EVGA GTX 470
Secondary: Reference 8600 GTS
PSU: OCZ ModXStream 700 watt

I ran the secondary card in the 3rd pcie slot at the bottom, and everything was fine.

I decided to upgrade to SLI 470s because i found a deal on another, even though it was a 470 SC. So I updated the following:

PSU: Seasonic SS-850HT
Secondary: EVGA GTX 470 SC

I put the new card in the proper slot for sli, and tried all orders and combinations of driver uninstalls/reinstalls but no matter what the output would go to the SC regardless of whether it was in the first slot or second. I did a mobo bios update, and they both magically started working, but upon turning it on the next day, same deal. No matter what i tried i could not get the non sc to show up in windows while the SC was present.

So i swapped in the following:
Proc: i3 540
Mobo: MSI P55-GD65

Same deal, but the BIOS update trick didnt work this time. Ended up downloading an update for "Realtek PCIe GBE family controller" through windows update, and after the reboot, Everything worked. I had had my pc on for a couple of weeks since then, but there was a power blink last night, and my non SC was once more unrecognized. I have tried cleaning out those realtek drivers and reinstalling, but alas, it wont solve my issue. I also decided to flash a SC bios onto my non SC to see if that was the issue. the card with the flashed bios works fine by itself, but once more if the SC card is present, it will not show up in device manager in windows, or output on any display hooked up to it. have tried all combinations of graphics driver cleans/reinstalls with all combinations of cards in slots at different points during the process(one at a time, both at the same time, etc..) When both have been recognized in windows, sli works fine, and i can switch between sli, surround and multi monitor mode fine.

TL; DR: I have 2 GTX 470's and am only able to get one to display in windows at a time.

Feel free to ask any questions if I am unclear about something. Once again, I have thoroughly troubleshot this and it is not a mobo or graphics card problem. Something is up with windows I'm guessing.

 

[Tiporaro]

A prelim search of google for that MSI board showed a few other users with inconsistent sli problems, but I'm not sure that I saw any cut and dry answer unfortunately. If you run GPU-Z I'm assuming it doesn't show up either as you're not seeing it in device manager. Also, I know its a random shot, but maybe double check your extra psu connections to the cards. Intermittent issues like this almost seem like a power issue, so you could even try troubleshooting the psu.

 

[_cp]

Your assumption about GPU-Z is correct, only the SC shows when both are in place. I have kept the 2x 6pin connectors for each card exclusive to each PCIe slot throughout all of this, so i tried a quick swap with different combinations, and it's the same. Both fans spin regardless, but only the real SC is displayed in windows. Also, the bios splash is always displayed on the first monitor hooked up to the SC. It seems odd to me, but I don't know why both of these motherboards would refuse to see my original 470 in a dual configuration. Both of these motherboards are RMA replacements for the old ones i had. I wanted to think it was a problem with running a superclocked version of the card with a non superclocked, but after flashing the bios to match the superclocked card, they are identical in GPU-Z and the problem persists. I found several others with my same problem, but the majority go unresolved, and I have already tried everything from the resolved ones i found (Downloading the realtek driver, flashing the mobo bios, every conceivable order of driver installation, etc.) others problems are also varied with their hardware. I have found people with the same problem using asus and gigabyte boards, and many other nvidia card configurations from 7800 sli to 480 sli. I have also tested everything with and without the sli bridge, and have tested the sli bridge that came with each board. I am just completely at a loss as to what could be wrong.