View Full Version : USB power

Aug 6, 2011, 10:08 PM
Ok guys I'm running into something very weird...I bought a buffalo external cd/DVD drive that is Mac compatible and no problems on my 2010 MBA when I had it. I gave that to my sister And got the 2011 and it does not have enough power the light goes red. The cd drive does have a second USB for what they call "boost mode" and when I plugged that in it had enough power. The problem is I had to use a USB power plug because the cord did not reach around to the other USB on the air. So I figure it might just be lion but then I try it on the 2010 MBA which is upgraded to lion and in 1 USB it worked fine. So do I have a flawed system? Or is this years less powerful? Appreciated all ideas. If you read this far thanks!

Aug 7, 2011, 12:01 AM
There is nothing wrong with your new 2011 MBA. Just because it worked with a single USB plug does not mean that it can be guaranteed to work on your new 2011 MBA with a single USB plug. The issue is not with your new MBA but with the fact that your external device needs more than 500mA of current. You got lucky that it worked with a single cable on your old MBA.

Some devices like high-speed external disk drives may require more than 500 mA of current and therefore cannot be powered from one USB 2.0 port. Such devices usually come with Y-shaped cable that has two USB connectors to be inserted into a computer. With such a cable a device can draw power from two USB ports simultaneously.