Method and apparatus for managing power consumption on a bus

An information storage device (10) includes a cartridge (14) removably inserted into a cradle (13) that has a drive module (18) releasably coupled to an interface module (17). The interface module can be operatively coupled by a cable (12) to a remote system. Communications through the cable conform to an industry-standard protocol. The storage device can receive power from either the cable or an external power source (31). The interface module can detect a change in the source of its operating power during normal system operation, and ensure that this is reported through the cable.