pcie Does PCIe link widths really matter for GPU?

Pomian · January 8, 2021

Hi,

I've been using the Phanteks Evolv Shift X case for some time. It has a small X470-I motherboard and a 2700X processor so the number of PCIe lanes is limited. I have two M.2 NVMe disks so for the graphics card I stay X8 instead of X16.

In the beginning I used the GTX 1080 Ti, now the RTX 3080. And that's all the time in the X8 and all in all, I don't notice any big drops in FPS (ignoring the CPU that currently limits the card).

How is it with link width, is it not using even half PCIe speed most of the time?

Enderman · January 8, 2021

There is no performance benefit over x8, it only matters for stuff like PCIe storage or network cards that can use that much bandwidth.

With PCIe 3.0 your GPU won't be bottlenecked at all.

Kisai · January 8, 2021

4 hours ago, Pomian said:

Hi,

I've been using the Phanteks Evolv Shift X case for some time. It has a small X470-I motherboard and a 2700X processor so the number of PCIe lanes is limited. I have two M.2 NVMe disks so for the graphics card I stay X8 instead of X16.

In the beginning I used the GTX 1080 Ti, now the RTX 3080. And that's all the time in the X8 and all in all, I don't notice any big drops in FPS (ignoring the CPU that currently limits the card).

How is it with link width, is it not using even half PCIe speed most of the time?

It matters, but usually not enough that other factors are more important. Generally for games, motherboards and GPU's are designed to operate at x8.

Please note the date here is 2016 on a 5th gen intel system (so DDR3): https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus

It would be interesting to see the same kind of benchmarks repeated with each year's hottest game, but it needs to be repeated that the bottleneck in terms of more performance is the GPU itself, so if you're buying a Geforce xx60 part, than no, a PCIe x16 link is likely going to have no bearing on the performance because the card itself can't achieve that performance. Meanwhile the xx90 xx80 and other high end GPU's probably can, but hit thermal limits before they can make use of that much bandwidth.