Target Disk Mode
Encyclopedia
Target Disk Mode is a boot mode unique to Macintosh
computers.
When a Mac that supports Target Disk Mode is started with the 'T' key held down, its operating system
does not boot. Instead, the Mac's firmware enables its drives to behave as a FireWire mass storage device.
A Mac booted in Target Mode can be attached to the FireWire port of any other computer - Mac or PC - where it will appear as an external FireWire device. Hard drives within the target Mac, for example, can be formatted, partitioned, etc., exactly like any other external FireWire drive. Some computers will also make their internal CD/DVD drives and other peripheral hardware available to the host computer via FireWire.
Target Disk Mode is useful for accessing the contents of a Mac which cannot be booted from its own operating system
. Target Disk Mode is the preferred form of old-computer to new-computer interconnect used by Apple's Migration Assistant.
and continued to offer it with most of the subsequent PowerBook
series and FireWire-equipped Macs. As long as the requisite software appeared in the system ROM
, the Mac could be booted into disk mode.
Originally called SCSI Disk Mode, a special cable (SCSI System Cable) allowed the original PowerBook series to attach to a desktop Mac as an external SCSI disk. A unique system control panel on the PowerBook was used to select a non-conflicting SCSI ID number from the host Mac.
This also made it possible to select the disk in the Startup control panel and boot up from it.
With the change to IDE drives starting with the PowerBook 150
and 190
, Apple implemented HD Target Mode, which essentially enabled SCSI Disk Mode by translating the external SCSI commands via the ATA
driver
. Officially reserved for Apple's portables only, all PowerBooks exclusively supported disk mode except the 140
, 145, 145B, 150
and 170
. However, SCSI Disk Mode can be implemented unofficially on any Macintosh with an external SCSI port, by suspending the startup process with the interrupt
switch, as long as its internal drive can be set to a different ID than the active host system's devices.
When Apple dropped the SCSI interface starting with the PowerBook G3, FireWire Target Disk mode replaced the earlier disk mode implementation. Further, TDM now officially supports all desktop models as well as the portable lines, if equipped with FireWire ports. In addition to the previously mentioned 68K PowerBooks, the only Macs which do not provide for any kind of disk mode (supported or otherwise) are the original iMac and iBook
series, the MacBook Air
, the late-2008 aluminium MacBook
and the late-2009 MacBook
, all of which also lack a FireWire port.
Thunderbolt does support Target Disk Mode
Note that this list includes all Macintosh computers introduced after July 2000, excluding only MacBooks with no FireWire port – the MacBook Air and some MacBooks (13-inch, Aluminum/plastic unibody).
The host computer may run Microsoft Windows
, but with some possible shortcomings: to read a Mac's HFS-formatted disks, extra drivers are necessary. With Mediafour's MacDrive, users are able to natively read and write, from within Windows's Explorer, HFS+ file systems. Aside from having MacDrive installed, users also must ensure their computer possesses 1394 ports in order to utilize Target Disk Mode methods. MacDrive also has a read-only option to prevent any accidental editing of the computer in Target Disk Mode; however, this mode cannot be set after an HFS/HFS+ disk is mounted.
With the addition of HFS drivers into Apple's Bootcamp, it has also become possible for Macs running Windows to read (but not write) HFS partitions, without the purchase of software like MacDrive. Users have separated these drivers from the main Bootcamp install, and now also install on other Windows computers.
Running a kernel of 2.4.x, host computers running Linux are also able to read and write to a Mac's HFS or HFS+ formatted disks. Most modern user-friendlier distributions of Linux, such as Ubuntu
and Fedora Core, running kernels of 2.4.x or greater, most commonly, have this functionality pre-installed. However, since the Linux kernel now supports HFS and HFS+ file system manipulation, users without this functionality pre-installed typically have to just compile a supplementary driver and attempt to remount the HFS/HFS+ formatted file system.
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...
computers.
When a Mac that supports Target Disk Mode is started with the 'T' key held down, its operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
does not boot. Instead, the Mac's firmware enables its drives to behave as a FireWire mass storage device.
A Mac booted in Target Mode can be attached to the FireWire port of any other computer - Mac or PC - where it will appear as an external FireWire device. Hard drives within the target Mac, for example, can be formatted, partitioned, etc., exactly like any other external FireWire drive. Some computers will also make their internal CD/DVD drives and other peripheral hardware available to the host computer via FireWire.
Target Disk Mode is useful for accessing the contents of a Mac which cannot be booted from its own operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
. Target Disk Mode is the preferred form of old-computer to new-computer interconnect used by Apple's Migration Assistant.
History
Apple introduced disk mode access with the PowerBook 100PowerBook 100
The PowerBook 100 was a portable subnotebook personal computer manufactured by Apple Computer and introduced on October 21, 1991 at the COMDEX computer expo in Las Vegas, Nevada. Priced at US$2,300, the PowerBook 100 was the low-end model of the first three simultaneously-released...
and continued to offer it with most of the subsequent PowerBook
PowerBook
The PowerBook was a line of Macintosh laptop computers that was designed, manufactured and sold by Apple Computer, Inc. from 1991 to 2006. During its lifetime, the PowerBook went through several major revisions and redesigns, often being the first to incorporate features that would later become...
series and FireWire-equipped Macs. As long as the requisite software appeared in the system ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
, the Mac could be booted into disk mode.
Originally called SCSI Disk Mode, a special cable (SCSI System Cable) allowed the original PowerBook series to attach to a desktop Mac as an external SCSI disk. A unique system control panel on the PowerBook was used to select a non-conflicting SCSI ID number from the host Mac.
This also made it possible to select the disk in the Startup control panel and boot up from it.
With the change to IDE drives starting with the PowerBook 150
PowerBook 150
The PowerBook 150 was a laptop created by Apple Computer in 1994. It was the last member of the PowerBook 100 series to use the original case design, the most affordable of the series when introduced, and also the last consumer model. It was 8 MHz faster than its predecessor, the PowerBook 145B...
and 190
PowerBook 190
The PowerBook 190 and its companion PowerBook 190cs are laptop computers manufactured by Apple Computer as part of their PowerBook brand, introduced to the market in August 1995. The two models differ only in their screen: The 190 had a 9.5" greyscale display, while the 190cs featured a 10.4" color...
, Apple implemented HD Target Mode, which essentially enabled SCSI Disk Mode by translating the external SCSI commands via the ATA
AT Attachment
Parallel ATA , originally ATA, is an interface standard for the connection of storage devices such as hard disks, solid-state drives, floppy drives, and optical disc drives in computers. The standard is maintained by X3/INCITS committee...
driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
. Officially reserved for Apple's portables only, all PowerBooks exclusively supported disk mode except the 140
PowerBook 140
The PowerBook 140 was released in the first line of PowerBooks. It was the mid-range PowerBook, between the low-end 100 and the high-end 170. As with the PowerBook 170, and unlike the 100, this PowerBook featured an internal floppy drive. Codenames for this model are: Tim Lite, Tim LC,...
, 145, 145B, 150
PowerBook 150
The PowerBook 150 was a laptop created by Apple Computer in 1994. It was the last member of the PowerBook 100 series to use the original case design, the most affordable of the series when introduced, and also the last consumer model. It was 8 MHz faster than its predecessor, the PowerBook 145B...
and 170
PowerBook 170
The PowerBook 170 was released by Apple Inc. in 1991 along with the PowerBook 100 and the PowerBook 140. Identical to the 140, it was the high end of the original...
. However, SCSI Disk Mode can be implemented unofficially on any Macintosh with an external SCSI port, by suspending the startup process with the interrupt
Interrupt
In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
switch, as long as its internal drive can be set to a different ID than the active host system's devices.
When Apple dropped the SCSI interface starting with the PowerBook G3, FireWire Target Disk mode replaced the earlier disk mode implementation. Further, TDM now officially supports all desktop models as well as the portable lines, if equipped with FireWire ports. In addition to the previously mentioned 68K PowerBooks, the only Macs which do not provide for any kind of disk mode (supported or otherwise) are the original iMac and iBook
IBook
The iBook was a line of laptop computers sold by Apple Computer from 1999 to 2006. The line targeted the consumer and education markets, with lower specifications and prices than the PowerBook, Apple's higher-end line of laptop computers....
series, the MacBook Air
MacBook Air
The MacBook Air family is a line of Apple ultraportable Macintosh notebook computers.The first-generation MacBook Air was a 13.3"-only model, previously promoted as the World's Thinnest Notebook, introduced at the Macworld Conference & Expo on January 15, 2008. It featured a custom Intel Merom CPU...
, the late-2008 aluminium MacBook
MacBook
The MacBook was a brand of Macintosh notebook computers built by Apple Inc. First introduced in May 2006, it replaced the iBook and 12-inch PowerBook series of notebooks as a part of the Apple–Intel transition. Positioned as the low end of the MacBook family, the Apple MacBook was aimed at the...
and the late-2009 MacBook
MacBook
The MacBook was a brand of Macintosh notebook computers built by Apple Inc. First introduced in May 2006, it replaced the iBook and 12-inch PowerBook series of notebooks as a part of the Apple–Intel transition. Positioned as the low end of the MacBook family, the Apple MacBook was aimed at the...
, all of which also lack a FireWire port.
Thunderbolt does support Target Disk Mode
Compatible computers
- eMacEMacThe eMac, short for education Mac, was a Macintosh desktop computer made by Apple Inc. It was originally aimed at the education market, but was later made available as a cheaper mass market alternative to Apple's second-generation LCD display iMac....
(all models) - iBookIBookThe iBook was a line of laptop computers sold by Apple Computer from 1999 to 2006. The line targeted the consumer and education markets, with lower specifications and prices than the PowerBook, Apple's higher-end line of laptop computers....
(FireWire) and all models introduced after September 2000 - iMacIMacThe iMac is a range of all-in-one Macintosh desktop computers built by Apple. It has been the primary part of Apple's consumer desktop offerings since its introduction in 1998, and has evolved through five distinct forms....
(Slot Loading) with firmware version 2.4 or later - iMacIMacThe iMac is a range of all-in-one Macintosh desktop computers built by Apple. It has been the primary part of Apple's consumer desktop offerings since its introduction in 1998, and has evolved through five distinct forms....
(Summer 2000) and all models introduced after July 2000 - Mac miniMac MiniThe Mac Mini is a small form factor desktop computer manufactured by Apple Inc. Like earlier mini-ITX PC designs, it is uncommonly small for a desktop computer: 7.7 inches square and 1.4 inches tall. It weighs 2.7 pounds...
(all models) - Mac ProMac ProThe Mac Pro is a workstation computer manufactured by Apple Inc. The machines are based on Xeon microprocessors, but are similar to the Power Mac G5 they replaced in terms of outward appearance and expansion capabilities...
(all models) - MacBookMacBookThe MacBook was a brand of Macintosh notebook computers built by Apple Inc. First introduced in May 2006, it replaced the iBook and 12-inch PowerBook series of notebooks as a part of the Apple–Intel transition. Positioned as the low end of the MacBook family, the Apple MacBook was aimed at the...
(original white and black plastic models, not the aluminum or plastic unibody models) - MacBook ProMacBook ProThe MacBook Pro is a line of Macintosh portable computers introduced in January 2006 by Apple. It replaced the PowerBook G4 and was the second model, after the iMac, to be announced in the Apple–Intel transition...
(all models) - XServeXserveXserve was a line of rack unit computers designed by Apple Inc. for use as servers. When the Xserve was introduced in 2002, it was Apple's first designated server hardware design since the Apple Network Server in 1996...
(all models) - Power Mac G4Power Mac G4The Power Mac G4 was a series of personal computers that was designed, manufactured, and sold by Apple between 1999 and 2004. They used the PowerPC G4 series of microprocessors. They were heralded by Apple to be the first personal supercomputers, reaching speeds of 4 to 20 Gigaflops...
(AGP Graphics) with ATA drive - Power Mac G4Power Mac G4The Power Mac G4 was a series of personal computers that was designed, manufactured, and sold by Apple between 1999 and 2004. They used the PowerPC G4 series of microprocessors. They were heralded by Apple to be the first personal supercomputers, reaching speeds of 4 to 20 Gigaflops...
(Gigabit Ethernet) and all models introduced after July 2000 - Power Mac G4 CubePower Mac G4 CubeThe Power Mac G4 Cube was a small form factor Macintosh personal computer from Apple Inc. It was sold from 2000 to 2001. Its cube shape is reminiscent of the NeXTcube from NeXT, acquired by Apple in 1996. The machine was designed by Apple industrial designer Jonathan Ive...
- Power Mac G5Power Mac G5The Power Mac G5 is Apple's marketing name for models of the Power Macintosh that contains the IBM PowerPC G5 CPU. The professional-grade computer was the most powerful in Apple's lineup when it was introduced, widely hailed as the first 64-bit PC, and was touted by Apple as the fastest personal...
(all models) - PowerBook G3PowerBook G3The PowerBook G3 is a line of laptop Macintosh computers made by Apple Computer between 1997 and 2000. It was the first laptop to use the PowerPC G3 series of microprocessors...
(FireWire) - PowerBook G4PowerBook G4The PowerBook G4 are a series of notebook computers that were manufactured, marketed, and sold by Apple, Inc. between 2001 and 2006 as part of its PowerBook line. It uses the PowerPC G4 processor, initially produced by Motorola and later by Freescale, after Motorola spun off its semiconductor...
(all models)
Note that this list includes all Macintosh computers introduced after July 2000, excluding only MacBooks with no FireWire port – the MacBook Air and some MacBooks (13-inch, Aluminum/plastic unibody).
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 Thunderbolt or FireWire port (either 400 or 800), or a FireWire port on a PC cardPC cardIn computing, PC Card is the form factor of a peripheral interface designed for laptop computers. The PC Card standard was defined and developed by the Personal Computer Memory Card International Association which itself was created by a number of computer industry companies in the United States...
- FireWire 2.3.3 or later
- Mac OSMac OSMac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
8.6 or later - An ATA hard drive at ATA bus 0.
The host computer may run Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
, but with some possible shortcomings: to read a Mac's HFS-formatted disks, extra drivers are necessary. With Mediafour's MacDrive, users are able to natively read and write, from within Windows's Explorer, HFS+ file systems. Aside from having MacDrive installed, users also must ensure their computer possesses 1394 ports in order to utilize Target Disk Mode methods. MacDrive also has a read-only option to prevent any accidental editing of the computer in Target Disk Mode; however, this mode cannot be set after an HFS/HFS+ disk is mounted.
With the addition of HFS drivers into Apple's Bootcamp, it has also become possible for Macs running Windows to read (but not write) HFS partitions, without the purchase of software like MacDrive. Users have separated these drivers from the main Bootcamp install, and now also install on other Windows computers.
Running a kernel of 2.4.x, host computers running Linux are also able to read and write to a Mac's HFS or HFS+ formatted disks. Most modern user-friendlier distributions of Linux, such as Ubuntu
Ubuntu (operating system)
Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...
and Fedora Core, running kernels of 2.4.x or greater, most commonly, have this functionality pre-installed. However, since the Linux kernel now supports HFS and HFS+ file system manipulation, users without this functionality pre-installed typically have to just compile a supplementary driver and attempt to remount the HFS/HFS+ formatted file system.