Efficency standards

[pyroim]

looking to build/ modify my current rig to make for better efficiency ( W/Mhs)
was looking at a possible 2+1 7770 set up due to 77W full load
2 would be in crossfire and be used for gaming when i need to game, third would be strictly for mining, any thoughts?

also! potential in increasing performance as the drivers mature?


also currently have a AMD 4100 under clocked with some cores disabled for sheer efficiency, dont know the current kw/h  or wattage at wall