Question I Had a Weird GPU Issue - x8 Instead Of x16

[Iron Woode]

I checked GPUz and it showed my Sapphire RX 6800 running at x8 4.0 instead of x16 4.0.

So I started checking the usual suspects: BIOS settings, NVMe ssd's, card seated correctly, etc

Everything seemed OK but then I decided to pull the card to really check it. The card was seated correctly but then I inspected the card itself and found something off. There was a mark on a gold contact so I used my magnifying glass to get a better look. There was a small black mark on there so I used some isopropyl alcohol on it and after a bit it looked normal. Re-installed the card and then rebooted the system and now GPUz says x16 4.0.

I can't see any performance difference so far.

 

[Jaskalas]

I can't see any performance difference so far.

You wouldn't typically. Unless benchmarking under specific conditions. Such as hitting the VRAM limit. Which your 16GB card is unlikely to encounter in 2025.

 

[ToTTenTranz]

Have you checked your motherboard's guide on M.2 installation and lane occupancy?

If you installed a M.2 in a certain slot that shares its lanes with the GPU's 16 lanes slot, it'll automatically take away from the available lanes for the GPU slot.

 

[DAPUNISHER]

Perhaps the black mark is from a tiny insect meeting their doom, and it disrupted contact?

 

[CP5670]

You wouldn't typically. Unless benchmarking under specific conditions. Such as hitting the VRAM limit. Which your 16GB card is unlikely to encounter in 2025.

There are some odd cases where it matters, like Metro Exodus with rt.

 

[DAPUNISHER]

There are some odd cases where it matters, like Metro Exodus with rt.

Do you recall where you saw those test? Interested in the methodology since Exodus is one of the best examples of a game that looks and runs great even with RT.

 

[CP5670]

NVIDIA GeForce RTX 4090 PCI-Express Scaling

The new NVIDIA GeForce RTX 4090 is a graphics card powerhouse, but what happens when you run it on a PCI-Express 4.0 x8 bus? In our mini-review we've also tested various PCI-Express 3.0, 2.0 and 1.1 configs to get a feel for how FPS scales with bandwidth.

www.techpowerup.com

Many boards will drop the main slot to 8x if certain M.2 slots are used, need to watch out for it and look in the manual carefully.

 

[Quintessa]

PCIe lanes are stupidly literal, every gold finger/contact matters. If one of the critical contacts (especially in the "lane negotiation" section at the start of the connector) is dirty, oxidized, or not making perfect contact, the link drops down to x8, x4, etc. No harm done, if the residue comes back, it could be flux residue, oxidation, or poor plating on the card.

 

[Iron Woode]

Have you checked your motherboard's guide on M.2 installation and lane occupancy?

If you installed a M.2 in a certain slot that shares its lanes with the GPU's 16 lanes slot, it'll automatically take away from the available lanes for the GPU slot.

NVIDIA GeForce RTX 4090 PCI-Express Scaling

The new NVIDIA GeForce RTX 4090 is a graphics card powerhouse, but what happens when you run it on a PCI-Express 4.0 x8 bus? In our mini-review we've also tested various PCI-Express 3.0, 2.0 and 1.1 configs to get a feel for how FPS scales with bandwidth.

www.techpowerup.com

Many boards will drop the main slot to 8x if certain M.2 slots are used, need to watch out for it and look in the manual carefully.

Yes, my M.2 drives are where they should be and their respective lanes.

Everything is back to normal now,