My 3,1 Mac Pro has no USB 3 ports so I thought I'd get a PCIe card to fill the gap. But it needs an extra cable to supply voltages missing on the PCIe bus. By the looks of it that's only 5V for port power. Threading a 4-wire disk power cable down from the unused one in the Optical Drive box seems like overkill. Can anyone confirm that the only voltage required is 5V, please? If so a single wire (or two) will suffice.