I have an ABIT mobo and have some new IDE cables. The mobo has 40 pins on its IDE connectors but my HDD, CDROM, Floppy and IDE cables have a pin missing to help figure out the orientation.

On page 4, there is an "IDE Power" connector. It looks a lot like a 4 pin CPU fan connector, but it (obviously) provides different voltages that are appropriate for 3.5" IDE drives (5V, 12V) and ...