Q&A: USB 2/3 autoconfigure confusion

Q Having just upgraded to a MacBook Pro, I was concerned to read Apple’s Q&A on its USB 3 ports. Is it true that they configure to the speed of the equipment that is first connected, so mine will now be stuck at USB 2 speeds?

A Do not fear: you have been confused by the ambiguous language used in Apple’s Q&A. Its original version was even more confusing, but even now it is far from clear.

The relevant sections state that USB 3 ports autoconfigure to the USB device that is connected “first”. By that it refers not to first in time, but closest in the chain of devices.

If you connect a chain, such as a USB hub and then a series of devices connected to that, the Mac port will see only the performance of the first link in that chain, the hub. If the hub is a USB 3 device, then your Mac will run that port at USB 3 speeds, even if the hub only has USB 2 devices connected to it. If instead you connect a USB 2 hub to the port on your MacBook Pro, then no matter what you connect to it, the Mac will only run USB 2 speeds to it.

Comments Although physically and electrically compatible, it is easy to confuse USB 2 and 3 cables and sockets. Standard products differ in the colour of the rectangular plastic insert inside the plug or socket: USB 2 can be any colour but is commonly white, whilst USB 3 should be blue (Pantone 300C).

However Apple, along with many manufacturers, does not use blue inserts in USB ports on its computers or other devices, presumably because of its overriding requirement for colour co-ordination.

Updated from the original, which was first published in MacUser volume 29 issue 6, 2013.