That psu includes 2 cables, each with 2 pcie connectors. Make sure you are using a single connector from each cable. I'm not sure that 1 cable can handle the full load required by high clock.
just to throw my 2 cents, but if the PSU is any good one PCIe cable should handle the power to the cube....some video cards can consume 250-300w easily....so 1 cable should do, it work for me on 3 cubes.
Agreed, but my measurements of the cube were 324 watts at high clock setting. Some have measured it at 350. That's really pushing the limits of a single cable, unless it's thick gauge.