I have the Nvidia GTX 680 GPU, and it has two 6 PIN power input connections..
My PSU has two PCI E power outputs. The PCI E cable itself is 8 PIN on one side, which of course will connect to the PSU, and on the other side of the wire, it's split into two 6+2 PIN connectors.
My question is, do I simply take the two "split" 6+2 PIN connectors and plug both of them into the two 6 PIN power inputs on the GPU, or would it be better to take two seperate PCI E cables, and run each directly from the PSU to the GPU?
13th I thought the same way and tried to power my GTX460 from my EA750W using only one wire. It wouldn't power up. I'm assuming each of the PCIe strands are on different rails and the PSU doesn't want you to use a lot from one while the other has no load.
Let us know the PSU, I am assuming that it is meant to plug into both slots on your GPU, if it does not come with more than 1 PCI-E cable I can't see any other solution, and especially if it does not have more than 1 output port for PCI. Post the PSU and it will be easier to determine, but I think you should be okay using each "half" of the Y into the single video card.
PS on further thought is this a modular PSU? I am guessing not, and on even further thought, posting your PSU will answer my question