Help understanding PCIe 16x/8x/16x/8x

[almandin]

Thanks for your answer NoReply.

I was looking at EPYC cpus at the moment. How do we know that running gpus at 4x is fine ? Was it all through trial and error approach ?

I guess its a waste of money then, to get an EPYC with 128 lanes and its associated (quite costly) motherboard when it could all run with 4x PCIe 4 slots ...