Right do you need to have both from the PSU if its on the motherboard? Im not sure if my PSU included with the case im getting will have the P4 cable
Yes you have to have the P4 cable if the motherboard requires it. The specs of the PS should say 'P4-Ready', 'P4-Compatible', or something like that to let you know is has the 12V P4 connector for the mobo.