Apparatus and techniques for awakening bus circuitry from an inactive state as needed are described. The bus circuitry forms part of a computer system and is placed in the inactive state (i.e., shut down) when not needed so as to conserve power. The bus circuitry is associated with a bus and can be awakened out of the inactive state when certain bus events, including resume, connect or disconnect, occur on the bus. The invention is particularly advantageous for computing devices (e.g., portable computers, desktop computers, server computers) where it is desirous to shut down bus circuitry as well as other circuitry (e.g., microprocessor) when not needed so as to reduce power consumption.