Target Disk Mode (sometimes referred to as TDM) is a boot mode for Macintosh computers wherein the Mac does not load the operating system, but instead behave as a FireWire mass storage device with the SBP-2 (Serial Bus Protocol) standard.

When booted to TDM, all of the computer's attached volumes (HFS+ volumes, MS-DOS volumes, DVD-ROM, etc.) appearing as devices attached to the hub. It is possible to daisy chain several Macs together by booting them each to Target Disk Mode. All of the volumes on all of the computers will be available to the host computer at the end of the chain.

Using Target Disk Mode

Target Disk Mode is activated by holding the T key on the keyboard instantly after powering on the computer. The Target Disk booted computer is then plugged into a host computer or other device via a FireWire cable. To shut it down, you simply eject the volume(s) from the host computer and then press the power button again.

Requirements for Target Disk Mode

Host computer requirements

The host computer (the computer into which the Target Disk Mode booted computer is plugged) must meet the following requirements:

Built-in FireWire port, or a FireWire port on a PC card

FireWire 2.3.3 or later

Mac OS 9 or later

It is also possible, though difficult due to idiosyncrasies in the way the TDM Mac emulates a mass storage device, to connect a Mac in Target Disk Mode to a Windows PC. It often works the first time a Mac in TDM is connected and fails on all subsequent attempts. By uninstalling the 1394 device from the Windows device manager, and then reinstalling it, the Windows PC will often recognize the Mac disk again.

Compatible computers

iMac (Slot Loading) with Firmware version 2.4 or later

iMac (Summer 2000) and all models introduced after July 2000

eMac (all models)

Mac mini (all models)

Power Mac G4 (AGP Graphics) with ATA drive

Power Mac G4 Cube

Power Mac G4 (Gigabit Ethernet) and all models introduced after July 2000

Power Mac G5 (all models)

iBook (FireWire) and all models introduced after September 2000

MacBook (all models)

PowerBook G3 (FireWire)

PowerBook G4 (all models)

MacBook Pro (all models)

Similar Utilities

On a non-Macintosh computer, the users can often share their internal drive using a Live CD, such as BART PE or Knoppix. This is not as convenient, but provides the means to copy files off an internal drive even if that drive does not contain a bootable operating system.

Notes


a b c "Target Disk Mode." Developer Connection. 16 Jan. 2002. Apple Computer Inc. 13 Jul. 2007.