I'm not sure now.... It was 270x or 7950.... Are they similar in hashing power?
On 7950 I have 2.2Mh/s on x13 algo. But my cards are pretty good underclocked

7950 is more similar to 280x than to 270x. Someone put settings for 280x few pages ago. Try them.
With gpu at 1080 I also had that, but when i changed into 1100 gpu, mem 1250, I have 2,6 mhash