And again meet bug with jumping speed. After 1,3 hour speed on all GPU's start to jump fron 0 to 1000 h/s and then stabilize on normal speed.
And it's need to fix overclock system hangs on Pitcairn. So as binary kernel slow down on 4Gb Pitcairn.

P.S. Yes, CPU usage is growing with time. At start it's only 0-1-2%. It's good. But after 1 hour it's allready 0-4%. And jumps continues to grow.