The new NVIDIA GeForce RTX 5090 is the first high-end graphics card that makes use of a PCI-Express 5.0 bus interface. Are you in trouble when try to run it on PCIe 4.0? What about x8, like when an SSD is using up some bandwidth? 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.
Tl;dr: You lose about 1% of performance going from PCIE 5.0 x16 to 4.0 x16.
That’s basically within the margin of error. It seems that for gaming on dGPUs, the PCIE 5.0 vs 4.0 isn’t really that important.
Meaning, since PCIe5 Mini-ITX boards still have a very limited selection and are still very expensive, i’ll be going with a 4er board in my future-proof gaming-sffpc. Btw, that with 1% was a year ago already, so no progress there.