OK... maybe i'm being dumb but there is nothing in the manuals about this. I have a BeQuiet L8 PSU with the Gigabyte Z68XP-UD3P which I'm in the process of installing now. The PSU has a cable which splits in to two, and I'm assuming both ends of this fit in to the motherboard connector? Seems odd why there are two though? And the CPU plugs are redundant I'm guessing? 
