Switch your driver to compute mode?
I didn't know that there is an option for this. That really helped, thank you!. Now it's 22.5 Mh/s. Is this a limit for this card or I can improve this without flashing BIOS?
You can only OC memory, or try to play with -dcri value
Also, try to put -asm 2 in command line, works better for some cards
Interestingly, if I increase OC memory even slightly, hashrate drops drastically. I tried increasing dcri in the compute mode, it didn't help (which is interesting too because it was helping in gaming mode). Also -asm 2 gave 16 Mh/s too. I couldn't understand this card, it should be very similar with other RX580's. I think I'm still missing some point, maybe voltage/power? It would be great if someone who has the same card gives an answer.