xubuntu power saving? Override needed on my system to avoid hash dropping

[erre]

Hi,

I have this problem: under xubuntu, my hashrate start good (750 kh with an r9280x) but, after a few minutes, start dropping. I downloaded amd-override-ctrl and found the clock rate jumping from the minimum (510) to the imposted values.
Setting 940-1600 as minimum clockrate using the override temporarly solved the issue, so i think it's related with some "power saving" thing. But i cant't get more than 650 kh/s this way.

Any clue or suggestion?