I have this card. I'm not a strapmeister. I can achieve 30+ with an explanation.
BIOS strapping 101: copy the 1750 strap over the higher straps. 28+ mh/s
Luck:
After reading all the relevant 580 threads, treasure can be found in the AMD rebrand thread that can get this card to 30+. But......, the drawback is that this card uses more power.
yes, I did it. all the other GPU got 31mh/s , except sapphire with hynix which are still 22mh/s.
sapphire with samsung did 31.
sapphire with elpida did 31.
xfx with samsung did 31.
xfx with hynix did 31.
ONLY sapphire with hynix did 22.... I tried it on 3 different GPU. All did 22...
Still don't know why.