Needs more juice.
The power requirements for 4 x 6770's is 1200W but its unlikely your PSU is capable of running that wattage, and especially not under full load 100% of the time.
The power requirements for 4 x 6770's is 1200W but its unlikely your PSU is capable of running that wattage, and especially not under full load 100% of the time.
It's a 6770! rebadged 5770
Running 4x6950 on a 650W PS, Measured VA at the plug = 700VA