Exactly thats why I asked if he uses newest soft

I with my 4 GPU 280x get 16,5 MHs

Have you bought a power meter to check your watts yet?
neeee

but
On my electricity power meter from provider of the electricity I used to have 1,1KW/h now have 1.0 on 3 GPU because 4th one didn`t undervolted.
On the 280x's, I found Nirvana (In Windoz) by doing the following:
- Reduce vddc to 1081mv for both performance clocks
- Take GPU clock down by 50, take Memory clock down according to original ratio. So if default is 1070/1550 use 1020/1475
- Take all Memory clocks down to 1475, even the non performance related clocks. (In VBE 7)
Depending on your cards you should have between 500 and 550 watts for a 4 card rig and speed of 15.5 Mh/s, temps around 57-58 degrees and fans are completely silent.
These are girlfriend friendly settings
