I've got 2 GTX 260's running on my P55 SLI motherboard. Both graphics cards work when plugged in individually to slot 1, (top slot directly below cpu), but the computer will not boot into windows (it'll post fine, but will get stuck on the part where the windows 7 logo appears) with either card plugged individually into slot 2.

When both cards are plugged into slots 1 and 2, the card plugged into slot 1 will work, but the card plugged into slot 2 will not be recognized - device manager shows:

"This device is not working properly because Windows cannot load the drivers required for this device. (Code 31)"

When both cards are plugged into slots 1 and 3, both cards are recognized, but apparently slot 3 is only a PCI-E x4 slot and isn't meant to be used for this purpose.


Should I rma my motherboard?

please advise

- will

well even when I plug them in slots 1 and 3, there is no option to enable SLI in the nvidia control panel. I've tried all sorts of things, rolling back the graphics driver as far as 195.62 and uninstalling the evga network adapter driver, to no avail, so I'm guessing the SLI option is not there because it's not supported with one card in a PCI-E x4 slot.

RBIEZE

You must run the cards in slot 1 and 3 for Sli.
Also make sure you use the sli bridge.

I would also recommend reinstalling the drivers jf you have issues with enabling sli with both cards in slot 1 and 3.

are you sure? I read in the online pdf manual that "For SLI use, it is very important to use only slots PCI Express Slots 1 and 2 (primary and secondary) for optimal performance".


On the motherboard, the top slot is marked "PCIE_X16_1", the one below is marked "PCIE_X8_2", and the one below that is marked "PCIE_X4_3".

Your cards should be installed like this for sli.