MSI 970A-G46 only enabling one graphics card

[jas88]

I built a new machine (parts from Scan - MSI 970A-G46 motherboard, two Palit nVidia GTX 680 graphics cards). Plenty of power (quad 12V rail, 4x25A; both 6 and 8 pin PCIe power to each card).

Only one of the two graphics cards gets enabled each time (usually but not always the one further from the CPU, in GPU slot 2). Windows (8 x64) Device Manager only shows one card, not both.

Ideas anyone? I could understand if one card were faulty, or one motherboard socket ... but only one of the two working at any time? BIOS bug?

[scaryjim]

what make is your power supply? Just because it has a big number on the side doesn't mean it can actually provide good clean power Given it has 4 PCI-e connectors it's likely to be OK, but that'd be the first thing to check on. Also check if the PCIe connectors connect to specific 12v rails - it could be that you're only loading one rail which would cause issues.

Check all the settings in the BIOS to make sure there's nothing you need to enable to allow 2 graphics cards to be used. Do you have any other PCIe cards plugged in? Some motherboards share PCIe lanes between slots so if you have multiple cards plugged in some take precedence, or the link width drops to x1 for the longer slot - this might have an impact.

But essentially, there's too many variables to come up with any really good ideas based on the information given, I'm afraid...

[jas88]

Turned out to be a faulty card (at least, RMAing it got me a working setup!) - strange, the card was alive enough to show up at least once, otherwise I'd have gone straight to "must be a duff card".

There were just the two PCIe cards, and I did wonder for a while about BIOS settings for enabling SLI, but no, just a dud card. On the bright side, Scan are pretty good at RMA handling!