<s>
Target	B-Device
Disk	I-Device
Mode	I-Device
(	O
sometimes	O
referred	O
to	O
as	O
TDM	O
or	O
Target	B-Device
Mode	I-Device
)	O
is	O
a	O
boot	B-Operating_System
mode	O
unique	O
to	O
Macintosh	B-Device
computers	O
.	O
</s>
<s>
When	O
a	O
Mac	O
that	O
supports	O
Target	B-Device
Disk	I-Device
Mode	I-Device
is	O
started	O
with	O
the	O
'	O
T	O
 '	O
key	O
held	O
down	O
,	O
its	O
operating	B-General_Concept
system	I-General_Concept
does	O
not	O
boot	B-Operating_System
.	O
</s>
<s>
Instead	O
,	O
the	O
Mac	O
's	O
firmware	O
enables	O
its	O
drives	B-Device
to	O
behave	O
as	O
a	O
SCSI	B-Architecture
,	O
FireWire	B-Protocol
,	O
Thunderbolt	B-Protocol
,	O
or	O
USB-C	O
external	O
mass	B-Device
storage	I-Device
device	I-Device
.	O
</s>
<s>
A	O
Mac	O
booted	O
in	O
Target	B-Device
Mode	I-Device
can	O
be	O
attached	O
to	O
the	O
port	O
of	O
any	O
other	O
computer	O
,	O
Mac	O
or	O
PC	O
,	O
where	O
it	O
will	O
appear	O
as	O
an	O
external	O
device	O
.	O
</s>
<s>
Hard	O
drives	B-Device
within	O
the	O
target	O
Mac	O
,	O
for	O
example	O
,	O
can	O
be	O
formatted	O
or	O
partitioned	O
exactly	O
like	O
any	O
other	O
external	O
drive	O
.	O
</s>
<s>
Some	O
computers	O
will	O
also	O
make	O
their	O
internal	O
CD/DVD	O
drives	B-Device
and	O
other	O
internal	O
and	O
external	O
peripheral	O
hardware	O
available	O
to	O
the	O
host	O
computer	O
.	O
</s>
<s>
Target	B-Device
Disk	I-Device
Mode	I-Device
is	O
useful	O
for	O
accessing	O
the	O
contents	O
of	O
a	O
Mac	O
which	O
cannot	O
load	O
its	O
own	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Target	B-Device
Disk	I-Device
Mode	I-Device
is	O
the	O
preferred	O
form	O
of	O
old-computer	O
to	O
new-computer	O
interconnect	O
used	O
by	O
Apple	O
's	O
Migration	O
Assistant	O
.	O
</s>
<s>
Neither	O
supports	O
USB	B-Protocol
;	O
however	O
,	O
Thunderbolt-to-Firewire	O
,	O
Thunderbolt-to-Gigabit-Ethernet	O
,	O
and	O
USB-3.0-to-Gigabit-Ethernet	O
adapters	O
are	O
an	O
option	O
when	O
one	O
of	O
the	O
computers	O
does	O
not	O
have	O
Firewire	B-Protocol
or	O
Thunderbolt	B-Protocol
.	O
</s>
<s>
Apple	O
introduced	O
disk	B-Device
mode	O
access	O
with	O
the	O
original	O
PowerBook	B-Device
100	I-Device
and	O
continued	O
to	O
offer	O
it	O
with	O
most	O
subsequent	O
PowerBook	B-Device
series	O
and	O
FireWire-equipped	O
Macs	O
.	O
</s>
<s>
As	O
long	O
as	O
the	O
requisite	O
software	O
appeared	O
in	O
the	O
system	O
ROM	B-Device
,	O
the	O
Mac	O
could	O
be	O
booted	O
into	O
disk	B-Device
mode	O
.	O
</s>
<s>
Target	B-Device
Disk	I-Device
Mode	I-Device
was	O
originally	O
called	O
SCSI	B-Architecture
Disk	B-Device
Mode	O
,	O
and	O
a	O
special	O
cable	O
(	O
SCSI	B-Architecture
System	O
Cable	O
)	O
allowed	O
the	O
original	O
PowerBook	B-Device
series	O
to	O
attach	O
to	O
a	O
desktop	O
Mac	O
as	O
an	O
external	O
SCSI	B-Architecture
disk	B-Device
.	O
</s>
<s>
A	O
unique	O
system	O
control	O
panel	O
on	O
the	O
PowerBook	B-Device
was	O
used	O
to	O
select	O
a	O
non-conflicting	O
SCSI	B-Architecture
ID	O
number	O
from	O
the	O
host	O
Mac	O
.	O
</s>
<s>
This	O
also	O
made	O
it	O
possible	O
to	O
select	O
the	O
disk	B-Device
in	O
the	O
Startup	O
control	O
panel	O
and	O
boot	B-Operating_System
up	I-Operating_System
from	O
it	O
.	O
</s>
<s>
With	O
the	O
change	O
to	O
IDE	B-Protocol
drives	I-Protocol
starting	O
with	O
the	O
PowerBook	B-Device
150	I-Device
and	O
190	B-Device
,	O
Apple	O
implemented	O
HD	O
Target	B-Device
Mode	I-Device
,	O
which	O
essentially	O
enabled	O
SCSI	B-Architecture
Disk	B-Device
Mode	O
by	O
translating	O
the	O
external	O
SCSI	B-Architecture
commands	O
via	O
the	O
ATA	B-Protocol
driver	B-Application
.	O
</s>
<s>
Officially	O
reserved	O
for	O
Apple	O
's	O
portables	O
only	O
,	O
the	O
mode	O
was	O
supported	O
by	O
all	O
PowerBooks	B-Device
except	O
the	O
140	B-Device
,	O
145	O
,	O
145B	O
,	O
150	B-Device
and	O
170	B-Device
.	O
</s>
<s>
However	O
,	O
SCSI	B-Architecture
Disk	B-Device
Mode	O
can	O
be	O
implemented	O
unofficially	O
on	O
any	O
Macintosh	B-Device
with	O
an	O
external	O
SCSI	B-Architecture
port	O
by	O
suspending	O
the	O
startup	O
process	O
with	O
the	O
interrupt	B-Application
switch	O
,	O
as	O
long	O
as	O
all	O
internal	O
drives	B-Device
on	O
the	O
chain	O
can	O
be	O
set	O
to	O
different	O
IDs	O
than	O
the	O
active	O
host	O
system	O
's	O
devices	O
.	O
</s>
<s>
When	O
Apple	O
dropped	O
the	O
SCSI	B-Architecture
interface	O
,	O
starting	O
with	O
the	O
AGP	B-Device
Power	I-Device
Mac	I-Device
G4	I-Device
and	O
“	O
Pismo	O
”	O
PowerBook	B-Device
G3	O
,	O
FireWire	B-Device
Target	I-Device
Disk	I-Device
mode	I-Device
replaced	O
the	O
earlier	O
disk	B-Device
mode	O
implementation	O
,	O
also	O
receiving	O
official	O
support	O
beyond	O
laptops	O
to	O
all	O
subsequent	O
Macs	O
with	O
built-in	O
Firewire	B-Protocol
.	O
</s>
<s>
Thunderbolt	B-Protocol
supports	O
Target	B-Device
Disk	I-Device
Mode	I-Device
.	O
</s>
<s>
The	O
12-inch	O
Retina	O
MacBook	B-Device
(	O
early	O
2015	O
)	O
has	O
only	O
one	O
expansion	O
port	O
,	O
a	O
USB-C	O
port	O
that	O
supports	O
charging	O
,	O
external	O
displays	O
,	O
and	O
Target	B-Device
Disk	I-Device
Mode	I-Device
.	O
</s>
<s>
Using	O
Target	B-Device
Disk	I-Device
Mode	I-Device
on	O
this	O
MacBook	B-Device
requires	O
a	O
cable	O
that	O
supports	O
USB	B-Protocol
3.0	O
or	O
USB	B-Protocol
3.1	O
,	O
with	O
either	O
a	O
USB-A	O
or	O
USB-C	O
connector	O
on	O
one	O
end	O
and	O
a	O
USB-C	O
connector	O
on	O
the	O
other	O
end	O
for	O
the	O
MacBook	B-Device
.	O
</s>
<s>
With	O
the	O
Mac	B-Device
transition	I-Device
to	I-Device
Apple	I-Device
silicon	I-Device
,	O
Apple	O
replaced	O
Target	B-Device
Disk	I-Device
Mode	I-Device
with	O
Mac	O
Sharing	O
Mode	O
.	O
</s>
<s>
Be	O
any	O
Macintosh	B-Device
except	O
the	O
following	O
models	O
:	O
</s>
<s>
The	O
host	O
computer	O
(	O
the	O
computer	O
into	O
which	O
the	O
Target	B-Device
Disk	I-Device
Mode	I-Device
booted	O
computer	O
is	O
plugged	O
)	O
merely	O
needs	O
to	O
meet	O
the	O
same	O
requirements	O
as	O
for	O
any	O
external	O
mass	B-Device
storage	I-Device
device	I-Device
using	O
the	O
bus	O
in	O
question	O
,	O
and	O
(	O
if	O
access	O
to	O
native	O
Mac	O
formatted	O
partitions	O
such	O
as	O
the	O
boot	B-Operating_System
volume	O
is	O
desired	O
)	O
support	O
for	O
the	O
correct	O
version	O
of	O
Hierarchical	B-Application
File	I-Application
System	I-Application
.	O
</s>
<s>
On	O
Classic	O
Mac	O
OS	O
,	O
this	O
means	O
FireWire	B-Protocol
2.3.3	O
or	O
later	O
and	O
Mac	O
OS	O
8.6	O
or	O
later	O
are	O
required	O
to	O
use	O
a	O
Firewire	B-Protocol
target	O
.	O
</s>
<s>
The	O
host	O
computer	O
may	O
run	O
Microsoft	B-Application
Windows	I-Application
,	O
but	O
with	O
some	O
possible	O
shortcomings	O
:	O
to	O
read	O
a	O
Mac	O
's	O
HFS-formatted	O
partitions	O
,	O
extra	O
drivers	O
such	O
as	O
MacDrive	O
,	O
TransMac	O
,	O
MacDisk	O
,	O
or	O
HFSExplorer	O
are	O
necessary	O
.	O
</s>
<s>
Users	O
also	O
must	O
ensure	O
their	O
computer	O
possesses	O
appropriate	O
interface	O
hardware	O
in	O
order	O
to	O
physically	O
connect	O
to	O
a	O
Mac	O
in	O
Target	B-Device
Mode	I-Device
.	O
</s>
<s>
MacDrive	O
also	O
has	O
a	O
read-only	O
option	O
to	O
prevent	O
any	O
accidental	O
editing	O
of	O
the	O
computer	O
in	O
Target	B-Device
Disk	I-Device
Mode	I-Device
;	O
however	O
,	O
this	O
mode	O
cannot	O
be	O
set	O
after	O
an	O
HFS/HFS	O
+	O
disk	B-Device
is	O
mounted	O
.	O
</s>
<s>
With	O
the	O
addition	O
of	O
HFS	B-Application
drivers	O
into	O
Apple	O
's	O
Boot	B-Application
Camp	I-Application
,	O
it	O
has	O
also	O
become	O
possible	O
for	O
Macs	O
running	O
Windows	O
to	O
read	O
(	O
but	O
not	O
write	O
)	O
HFS	B-Application
partitions	O
,	O
without	O
the	O
purchase	O
of	O
software	O
.	O
</s>
<s>
Users	O
have	O
separated	O
these	O
drivers	O
from	O
the	O
main	O
Bootcamp	B-Application
install	O
,	O
and	O
now	O
also	O
install	O
on	O
other	O
Windows	B-Application
computers	I-Application
.	O
</s>
<s>
Host	O
computers	O
running	O
Linux	B-Application
are	O
also	O
able	O
to	O
read	O
and	O
write	O
to	O
a	O
Mac	O
's	O
HFS	B-Application
or	O
HFS+	O
formatted	O
devices	O
through	O
Target	B-Device
Disk	I-Device
Mode	I-Device
.	O
</s>
<s>
It	O
is	O
working	O
out-of-the-box	O
on	O
most	O
distributions	O
as	O
HFS+	O
support	O
is	O
part	O
of	O
the	O
Linux	B-Application
kernel	O
.	O
</s>
