Two power supplies powering one computer?

Hi! i am asking if it is possible to use two power supplies to power your computer. for example, two 400w psu's. one to power two graphics cards, hard drives and cd drives. And one to power the motherboard and the rest of the accessories?
Update: i'm just really curious. or how about one power supply powering one graphics card and the motherboard while another power supply powering say another graphics card, the hard drive, dvd drive, fans, etc.
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