The MacBook 12″ does not offer Thunderbolt (and, by extension, FireWire), but Target Disk Mode is available over USB. This has meant that models which only offer USB connections, such as the 2008-2009 MacBook Air and MacBook, don’t offer Target Disk Mode. Target Disk Mode has only been available for Macs with Thunderbolt or FireWire (and, for you old-timers, PowerBook SCSI). To activate Target Disk Mode, you hold down the T key immediately after you turn on your Mac, before the Apple logo appears in the center of the screen.
This makes it easy to migrate data from one computer to another, perform disk repairs, or retrieve data from a Mac with a damaged operating system. Target Disk Mode has long been one of the Mac’s unique capabilities - it allows you to bypass the operating system entirely and access the internal drive directly, as though it were an external drive.
