Same GPU won't work in first PCIe slots in 2 different motherboards?

kissenger · 17 Feb 2015 at 01:40

So this is just really strange. About 2 months ago I thought my motherboard (an Asus Gene IV Z68) was broken because it wouldn't recognise my GPU (an MSI HD7970) in its main PCIe slot, but it did recognise it in the second PCIe slot. That's logical, right?

Well I sent my original motherboard off for RMA and in the mean time bought a replacement, an Asus Gene V Z77. So I put everything back together, with the GPU in the main PCIe slot and wouldn't you know it, not recognised again, but it is recognised in the second slot again!

Now either I'm the unluckiest person in the world and I've managed to get two different boards which both have the exact same fault (a dud main PCIe slot) or there is another problem here with my GPU or CPU or something else that I'm not spotting. Oh and just to add to the confusion, the motherboard I RMA'd has apparently been tested by the retailer and the fault I thought I identified has been confirmed.

Why in the world would a GPU refuse to work in the main PCIe slot of two different boards? Any help with this would be appreciated because I'm at the end of my tether due to still not having a working PC after 2 months.

pgi947 · 17 Feb 2015 at 07:31

Disable the igpu in bios.

You may need to plug your display cable into the motherboard first to get it to display, then either disable the on board gpu or set the primary display output to pcie.

Edit: definitely update the bios to the latest too, iirc many had issues with z68/77 and amd hd7000 series cards not displaying due to motherboard bios issues.

Shiari · 17 Feb 2015 at 08:08

You didn't forget to power the card, did you? Just making sure, I've done that

kissenger · 17 Feb 2015 at 10:56

Power is supplied, latest BIOS is installed... still no luck.

I can't find the option to disable the iGPU in BIOS. I know it's supposed to be in 'System Agent Configuration' but I don't seem to have that option under the 'Advanced' tab.

I also noticed that the GPU says 'running at x8 Native' in BIOS. I know the card is x16 native, and I think the second slot on the board is x16, so I'm not sure why it says that. The card runs fine in gaming. No noticeable difference in FPS, etc.

mmj_uk · 17 Feb 2015 at 11:23

The second slot is only wired for 8x you need to use it in the first slot for 16x, I'm not sure why it wouldn't be working in the top slot. If you clear the CMOS to default it should boot from the top slot if a GPU is there. Are you the plugging the monitor into the 7970 and not the motherboard?

eddyr · 17 Feb 2015 at 11:31

Do you have another CPU you could try in the board? Could be a problem with the pci-e controller on the CPU.

Have you checked there is nothing funky going on with the contact pads on the GPU? Maybe the rear half.

kissenger · 17 Feb 2015 at 12:22

Thanks for the replies. I did manage to get access to the iGPU controls in BIOS (they appeared after a reboot). There's no option to disable the iGPU but it does allow you to select the primary device and I've set it to PCIe, but it didn't work.

I've also cleared CMOS and no luck. Monitor is definitely plugged into GPU and I'm almost certain it's seated correctly because I've reseated several times with no luck, and it works fine in slot 2.

I don't have another CPU I can try. Once I've gone through all the suggestions in here I may have to look out for a 3570k or something like that on the MM.

savagesam117 · 17 Feb 2015 at 12:27

Like said before is everything being powered correctly? I know it may seem silly but I've done it before!

kissenger · 17 Feb 2015 at 12:35

savagesam117 said:
Like said before is everything being powered correctly? I know it may seem silly but I've done it before!

Yes, I've supplied it with the 6+2 and 6 pin connections. Fans are spinning so I think it is getting power.

mmj_uk · 17 Feb 2015 at 13:44

I would try to pick up a cheap second hand Celeron/Pentium to test with, it's always good to have a spare CPU sitting around in case of emergency anyway. The motherboard isn't shorting on the case is it? Do you have any other GPU's to try in the top slot?

geeko · 17 Feb 2015 at 14:25

Have you checked the underside of your CPU is clean? There might be a bit of crud stuck to a pin pad, preventing proper contact

nutsnut · 17 Feb 2015 at 16:28

Try reseating the CPU cooler? I've seen coolers tightened to much which causes problems with the RAM slots, perhaps it too could cause issues with the PCIe lanes.

kissenger · 17 Feb 2015 at 16:37

nutsnut said:
Try reseating the CPU cooler? I've seen coolers tightened to much which causes problems with the RAM slots, perhaps it too could cause issues with the PCIe lanes.

I will give that a shot, although I'm doubtful it will work in my case because when I was trying things on my previous board (the one I RMA'd) I did switch out my big cooler with the stock cooler at one point, and it didn't help.

Do you guys think it would be worth me switching to an earlier BIOS? I don't like messing with the BIOS any more than I have to but I wonder if that could help.

nutsnut · 17 Feb 2015 at 16:50

Also, might be a long shot but have you tried all output connections whilst the card is in the primary PCIe slot? It might be some weird bug where say just the DVI isn't outputting whilst in PCIe 1 slot, but HDMI/DP may work?

nutsnut · 17 Feb 2015 at 16:59

Kissinger, where about in Birmingham are you? If you want to try a different card in your board or your card in my MB then I may be able to help you out.

PS - I think i remember where you are located (i enquired about a KB you had for sale), drop me a PM if your interested.

kissenger · 17 Feb 2015 at 17:26

Thanks nutsnut. I have tried several different connections. I can't find my DVI lead but I've tried HDMI and micro-DP. I also just tried loosening the heatsink and while I was at it I tried different RAM configurations and neither worked.

That's very kind of you to offer. I'll drop you a PM.

muon · 17 Feb 2015 at 21:06

On the PCI-E 8x/16x issue, remember that Sandybridge chips only support PCI-E 2.

Not sure what it would end up looking like in the BIOS.

kissenger · 17 Feb 2015 at 21:16

muon said:
On the PCI-E 8x/16x issue, remember that Sandybridge chips only support PCI-E 2.

Not sure what it would end up looking like in the BIOS.

That would be why the 'NB PCIe configuration' section of the BIOS only has the options 'Auto', 'Gen1' and 'Gen2'. Also the fact that my GPU runs at x8 in the second slot is to be expected because only the top slot is x16. But I'm still at a loss as to why the card isn't recognised at all.

kissenger · 17 Feb 2015 at 23:28

I think I've pretty much ran out of ideas with this and it's going to come down to me obtaining a different CPU to try out, but I have just noticed one strange thing that might be an indication of what's wrong.

When the GPU is seated in slot 1, in the 'NB PCIe configuration' section of the BIOS it states 'x0' above the 'PCIEX16_1 Link Speed' option, but when it's taken out it reads 'Not present'.

So the board is clearly detecting something in that slot, even if it doesn't show up in Device Manager in Windows.

kissenger · 23 Feb 2015 at 17:33

Okay guys, thanks for your help so far. This is getting even more baffling...

I've just got hold of a second CPU and tried that out. The first time I booted with the new CPU my GPU in slot 1 was recognised. Then after a reboot it went back to not recognising it!

So that's two different motherboards, 2 different CPUs and the same issue where the GPU is recognised in the second PCIe slot, but not the first one. Is it safe to say at this point that the problem is with the GPU?

That's the only conclusion I can come to and yet I can't understand why a GPU would do that.