To my understanding, a gen3 x4 slot is equal to a gen2 x8 slot in terms of speed.
I assume that by default a gen3 card can not get full speed, because the gen3 card is only x4 physically, and therefore will only use half of an x8 slot. Plus potential protocol differences between gen3 and gen2.
But wouldn't it theoretically be possible to have an adapter condense x8 gen2 to x4 gen3?
Seemingly all information and posts about gen3 <> gen2 are just stating the obvious - that it pcie is backwards compatible, but nothing about using double the lanes. Nor was I able to find any adapters or something.
Is there no usecase for this? I would have imagined that people other than me want to put a gen3 network or storage cards into an older server that only has pice gen2.