Abstract: A peripheral device, such as a data storage device, is employed in a computer system having one or more computers. The computer system includes an interface architecture, such as Fiber channel or Serial Storage Architecture (SSA), providing a continuously clocked serial link. The data storage device includes a power supply and data storage components, such as disk drives, carried in a housing. One or more data communication interfaces, each of which is adapted for coupling with a computer through conductors, are carried on the housing and coupled to the data storage components. The data storage components have a substantially powered up state and a substantially powered down state which is entered in response to a power down signal. Detector circuitry is operative to detect a clock signal loss at each one of the data communication interfaces and to produce the power down signal responsive to the detection.