Can't get motherboard to detect 2nd GPU

[OgNasty]

I'm running 2 5970s with a 950 watt PSU on a MSI 870-G45 motherboard.  I can get the cards to work 1 at a time, but can't get the computer to detect the 2nd GPU.  I've confirmed it is not a power issue, not a cable issue...  Anyone have any suggestions?  I'm running the latest bios and win7 64-bit and the latest version of catalyst.  I've tried hooking up 2 monitors, switching which card is in which slot...  It's like the 2nd card doesn't exist as it won't even show up in device manager.  They'll both power up, but can't get detected.  The only thing I can think of is that the PCI-E slot on the motherboard is DOA.  I'm hoping it's just a software issue that you can help me with though.  Help!

[DeathAndTaxes]

What happens if you only have 1 card in the slot where 2nd GPU isn't detected?  If no GPU is detected it likely is the slot.

If a single GPU works in multiple slots then it isn't the slot.  Make sure the bracket (or GPU or case) isn't bent.  I once had a card with slightly bent bracket.  Just enough to prevent card from seating all the way.

[DeathAndTaxes]

What happens if you only have 1 card in the slot where 2nd GPU isn't detected?  If no GPU is detected it likely is the slot.

If a single GPU works in multiple slots then it isn't the slot.  Make sure the bracket (or GPU or case) isn't bent.  I once had a card with slightly bent bracket.  Just enough to prevent card from seating all the way.

No GPU is detected when only 1 card is in the "bad" slot and I get no video at all.

It's an open air rig so seating isn't a problem.  I'm using extender cables and I've confirmed they both work.

Temporarily try plugging 1 card DIRECTLY into "bad" slot.  If still nothing then I would be leaning towards bad slot.
If card works directly but not with extender then depending on the extender you may need to do the "short sense detect pins trick" (searching forum will find the thread).

[bronan]

i would first test boths the cards in that slot before trying anything else
thats what death and taxes meant by his post

if it works then you could buy a powered extender which seem to solve many problem with the cards you use
but again you need to know if the slot really works or not before spend money on a new extender
the powered extenders can be bought by cablesaurus as far as i know