You should be able to get 800+ on those cards each.
settings, please? I can't get over 740 with mine, MSI has been a much better performer for me than sapphire dual-x or gigabyte windforce
Dont belive every troll who doesnt know shit.
Your cards generally are not able to do clocks which are needed for 800+khs. You need minimum 1160/1800 for that.
Besides, pushing 280x to its limits not even closely efficent anymore. Those cards will consume way over 280W each and will be insanely hot when you push them like that. As a result fans would not survive over 3 months. Its a common flaw of several cards, If fans are running high rpms.