I’m having an issue where my RTX 4080 is only running at x8 PCIe Gen 4, as reported by GPU-Z and HWiNFO64. I’ve checked and ruled out BIOS or SSD issues because I tried another GPU (a 3060/ti) that worked at x16. I recently switched to an ASRock B850 motherboard, and I suspect the problem might be linked to the fact that I flashed my PNY GPU with a Zotac BIOS a couple of years back. I attempted to flash it to another BIOS recently, but it failed. I did manage to revert to the original BIOS from TechPowerUp, but the x8 issue persists. Any insights on what might be causing this?
2 Answers
From what I recall, the performance impact of running a 4090 on PCIe Gen 3 x16 is minimal—around 2-3% performance loss compared to Gen 4 x16. So if you’re only seeing 8 lanes, it might not be a massive deal on performance. Just make sure nothing else is using up your PCIe lanes, but it sounds like you’ve already looked into that.
First, make sure to check the CPU and motherboard specs. Sometimes, certain CPUs might limit PCIe lanes. Also, if your GPU isn’t seated properly or there’s debris in the PCIe slot, it could cause it to default to 8 lanes. Check your motherboard manual to see which M.2 slots share lanes with your PCIe x16 slot—especially if you have multiple SSDs. You might have to rearrange them or clean the slot as well. Lastly, some CPUs, especially lower-end AM5 chips, might only provide 8 lanes, so verify what CPU you’re using.
I checked, and the first PCIe slot isn’t affected by NVMe SSDs, and I’ve got a 9800X3D, so lane limitations shouldn’t be an issue. I’ll clean the slot just in case, but I’m not too hopeful.
Correct, I’ve double-checked, and the first PCIe slot should be fine regardless of the NVMe drives plugged in. It’s a bit baffling.