-v
EDIT: you sound like a noob so you had better read the OP (and whatever else you can get your hands on) ... and watch the temp.s if you are going to thrash these cards with mining or you'll fry your cores....
$aticonfig --adapter=all --odgt
get nervous with core temp above 80 C ... I keep mine 70 or below.
-v drop GPU consumption to 70 on average.
I've got few boxes with 2x5970 under archlinux and ubuntu, running for months and never have such problems like I've got with 6990, so I'm completely disoriented

And I keep temperature automatically by changing corerate