GPU not working on primary PCI-E Slot only secondary

[Nekrono]

You can refer to my original post here.

To avoid a long post the issue is this:

My video card (7970) stopped working all of a sudden, no video output on my monitor, tried several monitors/cables no luck.Tried different PSU and still nothing, yet the card worked as it booted up normally on a friends computer. I figure it must be the motherboard, I replaced the motherboard with a brand new one and the issue persists! I go back to the old motherboard and connected the card on the secondary PCI-E slot and it works!

At this point I'm thinking it's a huge coincidence that the primary PCI-E slots are dead on two motherboards, one of which is brand new so I had a friend borrow me his GTX 970 and plugged it in on my older mobo where the issue started on the primary PCI-E slot and it works flawlessy! Then I plugged in my 7970 without changing anything and NO VIDEO, however it works on the secondary slot though.

Why is the 7970 not working on the primary PCI-E and only on the secondary? Clearly the card and the mobo is fine. I haven't changed any settings. It hurts performance having the card running in the secondary slot since it's running at 4x not 16x. I don't understand why the 970 worked there but my 7970 is not.

 

[clutchc]

My guess is that whatever logic the last x4 lanes of the x16 slot operate on your card, are not functioning properly. But that doesn't explain why they work on your friend's x16 lanes. Bottom line: it's the card.

 

[tounz]

You can refer to my original post here.

To avoid a long post the issue is this:

My video card (7970) stopped working all of a sudden, no video output on my monitor, tried several monitors/cables no luck.Tried different PSU and still nothing, yet the card worked as it booted up normally on a friends computer. I figure it must be the motherboard, I replaced the motherboard with a brand new one and the issue persists! I go back to the old motherboard and connected the card on the secondary PCI-E slot and it works!

At this point I'm thinking it's a huge coincidence that the primary PCI-E slots are dead on two motherboards, one of which is brand new so I had a friend borrow me his GTX 970 and plugged it in on my older mobo where the issue started on the primary PCI-E slot and it works flawlessy! Then I plugged in my 7970 without changing anything and NO VIDEO, however it works on the secondary slot though.

Why is the 7970 not working on the primary PCI-E and only on the secondary? Clearly the card and the mobo is fine. I haven't changed any settings. It hurts performance having the card running in the secondary slot since it's running at 4x not 16x. I don't understand why the 970 worked there but my 7970 is not.

Sorry to bump an old thread but I am having this exact same issue, with the same card. My 7970 is behaving the same way, and I have tried in a friends x16 and it works, his 970 works on my mobo, but my card refuses to work in the primary pcie lane, only in the secondary x4 lane. Did you end up solving your problem my any chance?