Question Second GPU doesn't work

Feb 12, 2019
Hey, I have a pretty old PC with i7 4770 and my Mobo is b85-g34

I tried installing a second GPU. My new gpu is Rtx 2080 and my old gpu is GTX 1080.

Gtx 1080 is in the second PCI-e slot and when I connect a monitor to it, the monitor doesn't detect it. When I connect the monitor to RTX 2080 it works and boots up windows well but after a few minutes it shows a blue screen or freezes.

Each card works perfectly alone.I tried both cards in the first slot and they work well. There are problems only when I have them both connected at the same time.

BIOS detects both cards when they are connected to the mobo. Both slots glow in the bios settings.

RTX 2080 is connected to PCI-e x16
Second one is connected to PCI-e x8

This is what my motherboard says at least...

PSU is 1000W MR1000x corsair.

Now, with just RTX 2080 when openning geforce experience it crashes windows with blue screen but everything else works, I can play games, render 3d etc.

Is it even possible? My Mobo

Gen3 (16), Gen2 (4) "PCI-E GEN"

I want to connect a second GPU but my mobo gives x16 lanes to first slot so my second x4 slot won;t work. I want to downgrade to 8x lanes on my first PCIe slot.


So aside from the system crashing, why do you want both of those video cards in the system at the same time? Did you check for a BIOS update to the motherboard? If there is any PCIe lane adjustments you would find that in the BIOS options.

TJ Hooker

I want to connect a second GPU but my mobo gives x16 lanes to first slot so my second x4 slot won;t work. I want to downgrade to 8x lanes on my first PCIe slot.
I had already responded on this thread and your other one, but it looks like the forums bugged out or something and they're gone. To reiterate what I said in your other thread:
The two x16 slots don't share bandwidth. Even if you could force the first one to only run a x8, it wouldn't make a difference for the 2nd one. What graphics cards do you have, and what power supply?

Do both cards work in the 2nd slot if you leave the first slot empty?

TJ Hooker

You said that both cards work individually in the first slot, but did you ever try either of them individually in the 2nd slot by itself? Or any other add in card in the 2nd slot (e.g. wifi card)? So far we haven't established if the 2nd slot is even functional.
the cards wont sli and using the 1080 for physx only is both expensive and a waste of time.
as it stands the 2080 would be doing the grunt work while the 1080 sits there idling but supping power waiting for you to play a physx enabled title of which there are only about a dozen. other than that if your using it for compute performance/mining. theres no real reason to have both cards in the build as there different gens and as a result incompatible for gaming as a pair and wont add any performance.

so yeah dump the 1080 on ebay and recoup some of the cost of the 2080.. as thats about the only real use you will see from it...
in that case check the device manager and make sure the card is seen by the system
if so then refresh install the drivers with both cards installed. without removing the old driver.

attach the monitor to the 2080. and set the bios/eufi to peg 1 (the first pci-e slot)

if you attach the 1080 to pci-e slot 2 and plug that into the monitor you will need to set peg 2 as the default...

but even then he will likely have issues.

lastly if you then get a bsod post it her or look it up yourself.



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