a control circuit for booting a number of devices in a certain order includes two delay circuits and three switch circuits , the first switch circuit and the first delay circuit receiving a power good signal and a voltage signal from a power supply unit and thus allowing a first device to boot and the first delay circuit outputting a first delay signal after a set time , to the second switch circuit and the second delay circuit , which repeat the process of the first delay circuit and switch circuit , to boot the remaining devices .