If you have an older but good psu, you will find it wanting with the more modern motherboard. you can just plug in the four way into half the 8 way motherboard socket,and it should work. but it doesn't feel right. and you will have problems if you are pulling a lot of amps. This cable is the solution. it fills in the 8 way properly, but also supplies extra current by using a spare molex which your are bound to have. totally brilliant. simple as that.