Question Problems with Multi GPU setup ?

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CosmicEgg_

CosmicEgg_

Feb 25, 2025
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Hi guys,

I'm currently trying to setup a PC with both a GTX 1080 and an RTX 3090 Ti but i'm struggling to get it to work.

I tried many things but the current result is the 1080 booting with a code error 43 in device manager but work after a disabled enable and the 3090 Ti gets a code 45 and doesn't work at all.
Best I got was the 1080 working perfectly and the 3090 Ti showing up with no error but displaying nothing.

I can provide more informations on what I already tried and the result, I just don't that here it will be insanely long but I tried differents drivers, Windows reinstall, checked PSU, monitor and motherboard connections, etc.

Does someone have any ideas ?
 
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Yeah sorry I forgot these, my bad.

-ryzen 7 5800x
-asus x570 e gaming
-32go 4x8 ddr4 3600mhz
-asus 1080 o8g
-nvidia 3090ti fe
-corsair 850w (main psu)
-generic 650w (psu for the 1080 only)
-2 m.2 nvme
-win 10 (up to date)
 
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How are you sending the power on signal to the second PSU?

CosmicEgg_ said:
Well because I have multiples monitors and I have a useless 1080 otherwise. Why would it be hard ? Some people seem to just plug the cards and it's working
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Your newer GPU can easily handle more than one monitor. Sell the older one, or keep as a backup. You really don't need two GPUs.
 
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COLGeek said:
How are you sending the power on signal to the second PSU?


Your newer GPU can easily handle more than one monitor. Sell the older one, or keep as a backup. You really don't need two GPUs.
Click to expand...
Wire on the 2 pins of the 24pins. I just turn on this psu before the other and then hit the power button.

I know this GPU can handle more than 1 monitor but for some reasons I might end up with 5 monitors which this GPU can't handle. Even if it this useless I really want to be able to use the 1080
 
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I suspect the drivers are creating a ton of conflicts given the different hardware generations, each fighting to be the primary device and then failing due to driver conflicts.

You could try using DDU to remove ALL Nvidia drivers. Then install the 3090Ti (only it) and its drivers. If, after restart, everything is working. Install the 1080. No drivers. See if Windows auto-installs any drivers.
 
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It's what i'm trying right now. The only problem is : the 3090ti alone doesn't work. After the system boot into windows it display for a few second and after a bit of time or any input of my keyboard (not sure about that) the GPU stop displaying anything. Drivers are installed and are installed for the 3090 only
 
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COLGeek said:
That PSU is also powering the motherboard, right?

Assuming yes, do you have the 4-pin, 8-pin, and 24-pin power connections firmly attached to the motherboard AND the PSU?

What are you using to power the GPU? A Corsair cable or some other adapter cable?
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Yes it does.

Well I didn't connect the 4 pin assuming the 8 pin was enough for a 105w cpu. Is it requiered for a 3090ti ? 8 pin and 24 pin are firmly connected

I use oem corsair cables that came with the psu and the x3 8-pin to 12vhpwr included with the 3090ti fe
 
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In an old computer yes. Still had the same issue but integrated graphics took over so I was able to use windows. I'm beginning to think the 3090ti is the problem here but that would be the worst solution by far
 
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COLGeek said:
Then try testing with another (850w or better) PSU, if you can. No riser cable, for sure.
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I don't have any other computer right now nor another 850w or better. Also test it without the riser would be a pain to do, i'm running everything on custom watercooling. But the riser was tested on the other computer with an other GPU and it worked.
 
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I will try to test it in another pc asap but I don't have any other pc to do this right now.

Yes, I tried to put them both on gen3, then one on auto and the other and gen3 and other configurations but right now they're all setup to auto
 
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Might have found the problem. I bought the 3090ti from 2nd hand, and apparently the previously owner had put 2mm thermal pads instead of 1mm on the vram, resulting in not contact between the gpu die and the waterblock. I will fix this and do an update if it work
 
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CosmicEgg_ said:
Might have found the problem. I bought the 3090ti from 2nd hand, and apparently the previously owner had put 2mm thermal pads instead of 1mm on the vram, resulting in not contact between the gpu die and the waterblock. I will fix this and do an update if it work
Click to expand...
Yeah that's the usual, people have no idea what they are doing.

I hope he did not knock off some components there too trying to force all that together.
 
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