So here's my situation. Up until yesterday I was running a GTX 470 with a GTX 260 for dedicated PhysX. Everything worked perfectly, as it should. I ordered a second GTX 470 to SLI (P55, therefore dual @ 8x/8x). After taking the GTX 260 out, and seating the new GTX 470 and connecting the SLI bridge I powered up to find that only one GTX 470 was registering, on device manager AND MSI Afterburner (Of course this is after a driver uninstall and reinstall). The new card should have been detected right away by Windows in any case - which it wasn't.
Obviously my first reaction was to test the new card. So I took the old GTX 470 out, put the new one in by itself, did a clean driver install and found that it was working beautifully. Put the second GTX 470 (that is about 2 months old) and connected the SLI bridge, clean driver install etc., only to find the same problem - the second GTX 470 not working. OK, so that rules out that the cards are bad.
So I reverted back to my previous setup of the GTX 470 with dedicated GTX 260 for PhysX only to find that now the GTX 260 wasn't being detected either!
Extremely frustrating, and I'm under the assumption that my second PCI-Express slot has died after working well for over a month. Even with the GTX 260 or GTX 470 in the second slot, GPU-Z reports that the first GTX 470 is running at full 16x mode, indicating that the card isn't even being detected on a hardware level as in dual mode the 16 PCI-E lanes are divided in 2 with the P55 platform.
I flashed the BIOS to the latest, the system started randomly locking up after about 5 minutes. I've tried reinstalling Windows, and then putting both new cards in SLI with the bridge and reinstalling the drivers, nothing. The 2nd card still doesn't register, but both work PERFECTLY when put in the first slot. I also tried taking a card out the first slot and plugged the monitor to the card in the second slot and got no picture/
My PSU is strong and about a year and a half old, so it can't be that.
I've ordered myself the EVGA P55 FTW 200 (with the NF200 chip for full dual 16x/16x SLI - maybe a blessing in disguise ) - do you think that'll solve the problem?
My full spec's below;
Asus P7P55D-E Pro (SLI/CrossfireX support)
Intel Core i7 875K 2.93 GHz (was clocked at 3.4GHz before my motherboard croaked)
4Gb DDR3 (2x2Gb) OCZ Special Ops Edition 1600MHz Low Voltage RAM
2x Gigabyte GTX 470's soon to be in SLI (sold the GTX 260 today to pay for the new motherboard)
Corsair TX750W PSU (SLI certified)
It can't be the powersupply though because when I test the system with a GTX 470 in the first slot and the 2nd slot empty, it works fine. When I pull the card out of the 1st slot and put it into the 2nd slot while keeping the 1st slot empty, the monitor says it has signal but when I boot up there is no picture and it's as if Windows is starting normally.
On the upside, I'm really looking forward to the Evga P55 FTW 200 dual 16x/16x SLI on P55!