Question

GPU PCIe Lanes

So, it turns out that I've had my AMD Radeon Vega Frontier Edition plugged into a PCIe3 x8 slot the entire time have had it, when I COULD have installed it in an x16 slot. I primarily use the card for GPU assisted video rendering and cgi rendering. Am I losing any major performance on this particular GPU by only giving it 8 lanes, assuming that my CPU/motherboard have the bandwidth for up to 16 lanes for my GPU alone?

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Answer
No.

But some complain about single digit speed losses so for those, yes.

I can't find the articles about PCI 2.x versus 3.x and 8 or 16 lane changes so I'll peg it at single digit performance change most of the time.

I don't see any reason not to move the card. Is there a reason?

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Reason not to swap

The only reason I've hesitated to swap is because this particular machine is a bit of a network storage hub for our whole team, and is left on and running 24/7. The weekend is the best time to try out new configurations since no one needs that machine running except me. But that means working during the weekend--which I'll totally do if there's the possibility that I could gain us better stability and more render speed.

However, after poking around, it appears that GPU-Z is convinced that my GPU is in fact utilizing 16 lanes, so perhaps MSI was mistaken in their documentation, or perhaps I have a different sub-model, or perhaps that PCIe port was originally firmware locked to 8 lanes but was unlocked to 16 with a bios/firmware update...? I don't know. Maybe GPU-Z is confused.

If I'm truly using 16 lanes in the current port, it is admittedly more convenient than moving it to my top slot, which would block access and airflow to my NVMe M.2 drive.

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Mixed bag.

Some PCs go unstable since the better slot means a slight increase in load. As to NVME M.2 and airflow I've only heard of a recent super high performance model that comes with a heatsink. Till then I've yet to find I need to keep it cooler than the rest of the machine.

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Answer
Test

Run a render using the x8 slot and time it.

Now run the same render using the x16 slot and time it.

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