Q&A: USB drawing too much power

Q After I had connected a new Belkin USB hub to the front port of my Mac Pro, I saw a warning message that it was drawing too much power. It only had an iPhone dock connected to it, which did not work. The message persisted even after connecting a power supply to the hub, and it remains today, though the hub has long since been disconnected. Have I damaged that USB port?

A USB ports are more limited in the power that they can deliver than FireWire, for example. Although external devices that try to draw excessive power should not cause physical damage to the port, the ports on some Mac models such as the Power Mac G5 seem prone to this issue; it may be that some Mac Pros can suffer similarly.

Shut your Mac down, remove its power lead, and leave it for a full minute. With no cables connected to the front USB ports, reconnect the power lead, wait for 10 seconds, and start it up again with the Shift key held down. You can also try zapping the PRAM by holding the Command-Option-P-R keys during startup, until you hear the startup chime again.

Comments USB 3 ports should be capable of 4.5 W, and less likely to encounter such problems. We will see.

Updated from the original, which was first published in MacUser volume 28 issue 19, 2012.