Improved techniques to recognize a power source on a peripheral bus and/or determine power available from the power source via the peripheral bus are disclosed. Typically, the peripheral bus is supported by a cable connected between a host device and an electronic device. In this case, the host device is a power source (e.g., power adapter or battery pack) and the cable is used to provide power from the power source to the electronic device. Hence, by understanding the power available from the power source, the electronic device can manage its power utilization so as to operate in a stable and reliable manner. The electronic device is, for example, a portable computing device. Examples of portable computing devices include a Portable Digital Assistant (PDA) and a portable media player.