Tested: Cycles GPU Rendering with PCIe x1 Risers (and RTX Optix support) - Technical Support - Blender Artists Community
RTX 2080 Ti SLI - x8/x8 vs. x16/x16 - YouTube
RTX 3080 on PCI-e 3.0 (x16 vs x8) | [H]ard|Forum
GPU running at x8 PCI-e instead of x16. GPU is seated in the 1st slot, tried seating in 2nd slot, then its running at 4x. Tried reinstalling drivers, tried adjusting some settings
PCIe 4.0 and PCIe 3.0 - Difference between x8 and x16 with the fastest cards - Where does the bottleneck begin? | Page 7 | igor'sLAB