these guys with rx 570/580 hashing below 1kh/s i think are doing it wrong. check your straps and oc.
all of my rx 570 hashes above atleast 1kh be it 4gb or 8gb. the only problem i have is micron, which i think is the worst in cn variants.
Agree, matches what we found as well. Haven't really found any card stuck below 1kh/s, except for Micron mem where we've been stuck around 860 h/s on some cards whatever we try for straps and clocks. Samsung by far the easiest, Hynix often also just a copy of lower-to-higher straps. And, I'm really not that good with straps, I should add.