A network interface card in a networked client computer includes a network interface circuit that decodes and then compares incoming network packet addresses to known address bit patterns, the decoding and comparing circuitry being powered at all times. Receipt and recognition of certain addresses means the client computer must be powered-on, even if manually switched OFF. When such a server-transmitted address is recognized, a power-on signal is issued to a power control unit that causes full operating power to be coupled to the client computer. In this fashion, a server can broadcast power-on signals to a plurality of networked client computers or workstations.