Ethereum mining r9 280x / HD 7970

Hello www,

I just set up my every day gaming pc as a mining rig with two HD 7970 @3gb RAM wich have the same chip as the r9 280x. I expected more but anyway they make some profit :)
Both cards are running around 12 mh/s each and the whole system uses 430 Watts.

Depending on the power cost per kWh I am able to make a profit around 20$ per month.

In relation to the rx cards my cards won't make that much profit. But as a beginner or testing rig its perfect because I can try out different miner.

Are there any bios mods for the HD 7970 ghz edition for a better mining performance?