Now on the 3090, 1219 memory clock, so 1219 * 8 * 2 = 19.5 gbps and to find bandwidth, 19.5 Gbps * 2 * 384 / 16 = 936 GB/s, 936 / 8 = 117 mhs on eth default clocks, + 20% memory overclock, 24 Gbps * 2 * 384 / 16 = 1152 GB/s, 1152 / 8 = 144 mhs on eth, possible yeah.
It's a little higher than supposed to be, probably stock overclocked version to get 122mhs.
https://wccftech.com/nvidia-geforce-rtx-3090-impressive-mining-performance-122-mhs-ethereum/So far, this is what we have on ethash.
3090 1499 / 117 = 12.8 usd per mhs
3080 699 / 95 = 7.3 usd per mhs
3070 499 / 56 = 8.9 usd per mhs
5700 400 / 56 = 7.1 usd per mhs
5600 xt 279 / 42 = 6.6 usd per mhs
5500 xt 199 / 28 = 7.1 usd per mhs
from the link..
The performance is based on stock numbers for the card
we'll see if my estimate 133.33mhs "efficient enough" tweak hits the spot...but still, it can probably do 150mhs at max tweak/power.
extra vram will consume extra power of course
at 133.33mhs x3 card rig will be 400mhs. comparable to x4 3080 rig, but much expensive. not worth the density vs x4 3080.
but if you think about it, it is still better purchase than "500mhs eth asic is 4689$ at 750w" hehe
extra vram will consume extra power of course