miner software optimization might get 3090 to 150mhs...hopefully 
No, Eth is memory bound, 3080 and 3090 have the same memory type and speed so the minor difference we will see would be due to 320 vs 384bit bus width. And this isnt on-die HBM, dont expect 90+ on anything.
1080 is 35mhs
1080ti is 50mhs
that's 42.8% difference between 1080 and 1080ti, both gddr5x
Umm ... the 1080 was a GP 104 with 256bit bus width. The 1080ti was a GP102 with 352 bit bus width, thats where the hash increase is coming from. That, and better binned memory that can clock higher.
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yeah, that means even 3080 and 3090 both have the same type of vram. other things can make the the other (3090) more faster than 3080, they have different bus width too.
I just said both have gddr5x but the other one is 42% faster, the statement itself implies that there are other factors too.
well you just have to read english more buddy.