Hi bitcointalk folks

I hope someone of you can point me in the right direction as to why my cards (R9 290) perform worse under xubuntu 12 than under win7.

Under win7 I get 850-900kh, there I installed catalyst and sdk and thats about it.
Under xubuntu 12 I cant manage to get past 700kh no matter if I take the same config like under win7 or if I tweak the hell out of it.
The installation procedure I did can be found here http://litecoinsblog.com/installing-radeon-r9-290-gpu-drivers-in-xubuntu-64bit/.

As you see no SDK in this guide mentioned ... well I gave it a try anyway after the low hash rate was killing my mood so I installed http://developer.amd.com/tools-and-sdks/heterogeneous-computing/amd-accelerated-parallel-processing-app-sdk/downloads/.
Result was that cgminer couldnt find any of my cards from that point on. Reinstalled catalyst etc nothing seemed to help, got creepy errors and stuff after which i reinstalled xubuntu from the bottom up.

My question is has anybody managed to reach 800-900kh under xubuntu and if so what were the steps? SDK yay, nay? I'm pretty sure its not the cgminer parameters for I have tried a lot (eg http://rumorscity.com/2013/12/03/litecoin-gpu-mining-with-amd-r9-290-and-r9-290x-sweet-spot-for-1000khashsec/) while on the win7 machine i just put -I 20 and all runs smoothly.

Greetings