The computer requiers quite a bit of +5V and +12V .. you should try get more than 1 cable to supply this to the motherboard or you might experience problems. If you look at the original PSU plug you see there are some cables that are far thicker than the other cables so that they can supply more power to the motherboard. Look at the motherboard plug of a PC and you will see that there are several cables that supply the same current, same reason.
