I'm currently using an X570 motherboard (MSI Prestige Creation) with a Ryzen 5900X and an RTX 5070 Ti. I want to expand my storage options but both M.2 slots on my motherboard are already occupied. I'm considering getting an M.2 PCIe 4.0 adapter or just going with a standard 2.5-inch SSD. My concern is that switching to a PCIe adapter will drop my GPU's PCIe lane count from x16 to x8, and I'm curious about how much this will impact GPU performance. I primarily do heavy 3D modeling, sculpting, and rendering, rather than gaming, so I want to ensure whichever storage solution I choose will best suit my workflow. Should I go for the PCIe adapter with an M.2 drive, or stick with a 2.5-inch SSD instead?
3 Answers
Even if you drop from x16 to x8 for the GPU, the change is typically just a few percent in performance. For most tasks, especially outside of gaming, you shouldn't notice a significant dip at all.
The PCIe bandwidth reduction shouldn’t have a major impact on your performance, especially for most 3D modeling tasks. Generally, unless you're constantly loading massive assets into VRAM, you should be fine. Most modeling software won't hit the bandwidth ceiling often, if at all.
Well, in my case, I'm mostly dealing with high poly models, often hitting 200 million polygons, which can utilize around 11 to 14GB of VRAM, so I do worry about asset loading.
In my experience, SSDs don’t need to max out PCIe lanes to perform well. If you're using both slots, just be aware that your GPU will switch to x8, but it shouldn't create any bottlenecks for your tasks.
So when both slots are utilized, the GPU automatically drops to x8? That's what I was worried about.

Thanks for the reassurance, that's good to know!