Under linux OS like smos and hiveos I get 27-28 Mh for 280x. There is only one tweak in the config that I've made under Ubuntu and that is the set parameters for the virtual memory. The only drawback is the power - around 180-200W vs. 90W for 1060 which get 23 Mh.
Are You talkkng about R9 280x 3GB ? I have few of them and my max is 12.6 MH/s
usung 5.3c + Windows 10 + driver 20.4.x
https://prnt.sc/vu5tjqDo You think that on linux is chance to get more ?
Yes, under linux 280x 3Gb Tahiti get 26-28 Mh/s. With ETC. I also have rare 280x with 6Gb Vram, which also get 26 Mh. Tonight phoenix stopped working with hawaii and tahiti for ETH, but at least for my cards lolminer is working with tahiti. For some strange reason for hawaii it is working on half of my cards with 20 Mh instead of 30, and it can't load DAG on some of them, although they are 8Gb. So I am sticking with phoenix mining ETC for hawaii, until developers comile new kernels for these cards.