170h/s on a reference 290? I'm seeing 200 at 1030/1250 -100mv with the stock bios, if I go to 1100/1475 it just eats power for an extra 10h/s.
Reference 290 can hash at 230 h/s @ 1100/1450 with Stilt BIOS mods.
More with Hynix mem
Even more with 290X.