<s>
The	O
Macintosh	B-Device
External	I-Device
Disk	I-Device
Drive	I-Device
is	O
the	O
original	O
model	O
in	O
a	O
series	O
of	O
external	O
-inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
manufactured	O
and	O
sold	O
by	O
Apple	O
Computer	O
exclusively	O
for	O
the	O
Macintosh	B-Device
series	O
of	O
computers	O
introduced	O
in	O
January	O
1984	O
.	O
</s>
<s>
Later	O
,	O
Apple	O
would	O
unify	O
their	O
external	O
drives	O
to	O
work	O
cross-platform	O
between	O
the	O
Macintosh	B-Device
and	O
Apple	B-Device
II	I-Device
product	O
lines	O
,	O
dropping	O
the	O
name	O
"	O
Macintosh	B-Device
"	O
from	O
the	O
drives	O
.	O
</s>
<s>
Though	O
Apple	O
had	O
been	O
producing	O
external	B-Device
floppy	I-Device
disk	I-Device
drives	I-Device
prior	O
to	O
1984	O
,	O
they	O
were	O
exclusively	O
developed	O
for	O
the	O
Apple	B-Device
II	I-Device
,	O
III	B-Device
and	O
Lisa	B-Device
computers	O
using	O
the	O
industry	O
standard	O
-inch	O
flexible	B-Device
disk	I-Device
format	O
.	O
</s>
<s>
The	O
Macintosh	B-Device
external	O
drives	O
were	O
the	O
first	O
to	O
widely	O
introduce	O
Sony	O
's	O
new	O
-inch	O
rigid	O
disk	B-Device
standard	O
commercially	O
and	O
throughout	O
their	O
product	O
line	O
.	O
</s>
<s>
Apple	O
produced	O
only	O
one	O
external	O
-inch	O
drive	O
exclusively	O
for	O
use	O
with	O
the	O
Apple	B-Device
II	I-Device
series	O
called	O
the	O
Apple	O
UniDisk	O
3.5	O
.	O
</s>
<s>
The	O
original	O
Macintosh	B-Device
External	I-Device
Disk	I-Device
Drive	I-Device
(	O
M0130	O
)	O
was	O
introduced	O
with	O
the	O
Macintosh	B-Device
on	O
January	O
24	O
,	O
1984	O
.	O
</s>
<s>
The	O
drive	O
case	O
was	O
designed	O
to	O
match	O
the	O
Macintosh	B-Device
and	O
included	O
the	O
same	O
400-kilobyte	O
drive	O
(	O
a	O
Sony-made	O
-inch	O
single-sided	O
mechanism	O
)	O
installed	O
inside	O
the	O
Macintosh	B-Device
.	O
</s>
<s>
Although	O
very	O
similar	O
to	O
the	O
400-kilobyte	O
drive	O
which	O
newly	O
replaced	O
Apple	O
's	O
ill-fated	O
Twiggy	B-Device
drive	I-Device
in	O
the	O
Lisa	B-Device
,	O
there	O
were	O
subtle	O
differences	O
relating	O
mainly	O
to	O
the	O
eject	O
mechanism	O
.	O
</s>
<s>
The	O
Macintosh	B-Device
could	O
only	O
support	O
one	O
external	O
drive	O
,	O
limiting	O
the	O
number	O
of	O
floppy	B-Device
disks	I-Device
mounted	O
at	O
once	O
to	O
two	O
,	O
but	O
both	O
Apple	O
and	O
third	O
party	O
manufacturers	O
developed	O
external	O
hard	O
drives	O
that	O
connected	O
to	O
the	O
Mac	O
's	O
floppy	B-Device
disk	I-Device
port	O
,	O
which	O
had	O
pass-through	O
ports	O
to	O
accommodate	O
daisy-chaining	O
the	O
external	O
disk	B-Device
drive	I-Device
.	O
</s>
<s>
Apple	O
's	O
Hard	B-Device
Disk	I-Device
20	I-Device
could	O
accommodate	O
an	O
additional	O
daisy-chained	O
hard	B-Device
drive	I-Device
as	O
well	O
as	O
an	O
external	O
floppy	B-Device
disk	I-Device
.	O
</s>
<s>
3.5-inch	O
single-sided	O
floppies	B-Device
had	O
been	O
used	O
on	O
several	O
microcomputers	O
and	O
synthesizers	O
in	O
the	O
early	O
1980s	O
,	O
including	O
the	O
Hewlett	O
Packard	O
150	O
and	O
various	O
MSX	B-Operating_System
computers	O
.	O
</s>
<s>
The	O
standard	O
on	O
all	O
of	O
these	O
was	O
MFM	B-Protocol
with	O
80	O
tracks	O
and	O
9	O
sectors	O
per	O
track	O
,	O
giving	O
360KB	O
per	O
disk	B-Device
.	O
</s>
<s>
However	O
,	O
Apple	O
's	O
custom	O
interface	O
uses	O
Group	B-Device
Coded	I-Device
Recording	I-Device
(	O
GCR	B-Device
)	O
and	O
a	O
unique	O
format	O
which	O
puts	O
fewer	O
sectors	O
on	O
the	O
smaller	O
inner	O
tracks	O
and	O
more	O
sectors	O
on	O
the	O
wider	O
outer	O
tracks	O
of	O
the	O
disk	B-Device
.	O
</s>
<s>
The	O
disk	B-Device
speeds	O
up	O
when	O
accessing	O
the	O
inner	O
tracks	O
and	O
slows	O
down	O
when	O
accessing	O
the	O
outer	O
ones	O
.	O
</s>
<s>
This	O
is	O
called	O
the	O
"	O
Zoned	O
CAV	O
"	O
system	B-Application
;	O
there	O
are	O
five	O
zones	O
of	O
16	O
tracks	O
each	O
.	O
</s>
<s>
This	O
allows	O
more	O
space	O
per	O
disk	B-Device
(	O
400KB	O
)	O
and	O
also	O
improves	O
reliability	O
by	O
reducing	O
the	O
number	O
of	O
sectors	O
on	O
the	O
inner	O
tracks	O
which	O
had	O
less	O
physical	O
media	O
to	O
allocate	O
to	O
each	O
sector	O
.	O
</s>
<s>
The	O
external	O
400-kilobyte	O
Macintosh	B-Device
drive	O
will	O
work	O
on	O
any	O
Macintosh	B-Device
that	O
does	O
not	O
have	O
a	O
high	O
density	O
SuperDrive	O
controller	O
(	O
due	O
to	O
electrical	O
changes	O
with	O
the	O
interface	O
)	O
,	O
but	O
the	O
disks	B-Device
in	O
practice	O
only	O
support	O
the	O
MFS	B-Application
file	O
system	B-Application
.	O
</s>
<s>
Although	O
a	O
400-kilobyte	O
disk	B-Device
may	O
be	O
formatted	O
with	O
HFS	B-Application
,	O
it	O
cannot	O
be	O
booted	O
from	O
,	O
nor	O
is	O
it	O
readable	O
in	O
a	O
Mac	B-Device
128	I-Device
or	O
512	O
.	O
</s>
<s>
Copy	O
protection	O
schemes	O
were	O
not	O
as	O
elaborate	O
or	O
widespread	O
on	O
Macintosh	B-Device
software	O
as	O
they	O
were	O
on	O
Apple	B-Device
II	I-Device
software	O
for	O
several	O
reasons	O
.	O
</s>
<s>
Also	O
Apple	O
did	O
not	O
publish	O
source	O
listings	O
for	O
the	O
Mac	B-Application
OS	I-Application
ROMs	O
as	O
they	O
did	O
with	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
Finally	O
,	O
the	O
Mac	B-Application
OS	I-Application
routines	O
were	O
considerably	O
more	O
complex	O
and	O
disk	B-Device
access	O
had	O
to	O
be	O
synchronized	O
with	O
the	O
mouse	O
and	O
keyboard	O
.	O
</s>
<s>
By	O
early	O
1985	O
,	O
it	O
was	O
clear	O
that	O
the	O
Macintosh	B-Device
needed	O
additional	O
storage	O
space	O
,	O
in	O
particular	O
a	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
Apple	O
announced	O
their	O
first	O
hard	B-Device
drive	I-Device
for	O
the	O
Mac	O
in	O
March	O
1985	O
.	O
</s>
<s>
However	O
,	O
the	O
MFS	B-Application
file	O
system	B-Application
did	O
not	O
support	O
subdirectories	O
,	O
making	O
it	O
unsuitable	O
for	O
a	O
hard	O
disk	B-Device
.	O
</s>
<s>
Apple	O
quickly	O
began	O
adopting	O
for	O
the	O
Mac	O
the	O
hierarchical	O
based	O
SOS	B-Operating_System
filing	O
system	B-Application
introduced	O
with	O
the	O
Apple	B-Device
III	I-Device
and	O
long	O
since	O
implemented	O
in	O
ProDOS	B-Operating_System
for	O
the	O
Apple	B-Device
II	I-Device
series	O
and	O
the	O
Lisa	B-Device
.	O
</s>
<s>
This	O
change	O
in	O
the	O
Mac	O
's	O
filing	O
system	B-Application
delayed	O
the	O
introduction	O
of	O
the	O
double	O
sided	O
Sony	O
drives	O
which	O
Apple	O
intended	O
to	O
offer	O
as	O
soon	O
as	O
the	O
technology	O
was	O
available	O
,	O
a	O
concession	O
they	O
made	O
when	O
adopting	O
the	O
Sony	O
drives	O
over	O
their	O
own	O
problematic	O
double-capacity	O
Twiggy	B-Device
drives	I-Device
.	O
</s>
<s>
However	O
,	O
based	O
on	O
the	O
success	O
of	O
the	O
3.5-inch	O
floppy	B-Device
drive	I-Device
for	O
the	O
Mac	O
,	O
there	O
was	O
no	O
such	O
obstacle	O
in	O
immediately	O
implementing	O
an	O
800-kilobyte	O
drive	O
for	O
the	O
Apple	B-Device
II	I-Device
,	O
so	O
it	O
was	O
introduced	O
in	O
September	O
1985	O
,	O
four	O
months	O
before	O
the	O
version	O
for	O
the	O
Mac	O
.	O
</s>
<s>
While	O
Apple	O
simultaneously	O
introduced	O
their	O
new	O
hard	B-Device
drive	I-Device
after	O
a	O
6-month	O
delay	O
,	O
they	O
chose	O
not	O
to	O
implement	O
the	O
new	O
floppy	B-Device
drive	I-Device
for	O
the	O
Macintosh	B-Device
at	O
that	O
time	O
.	O
</s>
<s>
In	O
September	O
1985	O
,	O
Apple	O
released	O
its	O
first	O
-inch	O
drive	O
(	O
A2M2053	O
)	O
for	O
the	O
Apple	B-Device
II	I-Device
series	O
utilizing	O
Sony	O
's	O
new	O
800-kilobyte	O
double-sided	O
drive	O
mechanism	O
,	O
which	O
would	O
not	O
be	O
released	O
for	O
the	O
Macintosh	B-Device
until	O
four	O
months	O
later	O
.	O
</s>
<s>
The	O
Apple	O
UniDisk	O
3.5	O
drive	O
contained	O
additional	O
circuitry	O
making	O
it	O
an	O
"	O
intelligent	O
"	O
or	O
"	O
smart	O
"	O
drive	O
;	O
this	O
made	O
it	O
incompatible	O
with	O
the	O
Macintosh	B-Device
,	O
despite	O
having	O
the	O
identical	O
mechanism	O
that	O
was	O
to	O
be	O
later	O
used	O
in	O
the	O
Macintosh	B-Device
drive	O
.	O
</s>
<s>
However	O
,	O
if	O
the	O
internal	O
circuit	O
board	O
(	O
which	O
consisted	O
of	O
its	O
own	O
CPU	B-Device
,	O
IWM	B-Device
chip	O
,	O
RAM	B-Architecture
and	O
firmware	O
)	O
was	O
bypassed	O
it	O
could	O
operate	O
on	O
a	O
Macintosh	B-Device
as	O
an	O
800-kilobyte	O
drive	O
.	O
</s>
<s>
This	O
permitted	O
storage-hungry	O
Mac	O
users	O
the	O
ability	O
to	O
double	O
their	O
disk	B-Device
capacity	O
5	O
months	O
before	O
Apple	O
officially	O
made	O
an	O
800-kilobyte	O
drive	O
available	O
for	O
the	O
Mac	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
the	O
HD20	O
Startup	O
disk	B-Device
came	O
with	O
HFS	B-Application
and	O
a	O
new	O
"	O
.Sony	O
"	O
driver	O
that	O
supported	O
800K	O
drives	O
(	O
in	O
addition	O
to	O
the	O
HD20	O
)	O
.	O
</s>
<s>
Ironically	O
,	O
though	O
the	O
drive	O
would	O
prove	O
to	O
be	O
significantly	O
faster	O
than	O
the	O
previous	O
400-kilobyte	O
drive	O
,	O
it	O
was	O
specifically	O
slowed	O
down	O
to	O
accommodate	O
the	O
slower	O
1-megahertz	O
processor	O
of	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
It	O
plugged	O
in	O
directly	O
to	O
the	O
Apple	O
IIc	O
disk	B-Device
port	O
(	O
although	O
original	O
IIcs	O
needed	O
a	O
ROM	B-Device
upgrade	O
)	O
and	O
required	O
a	O
specialized	O
interface	O
card	O
on	O
earlier	O
Apple	B-Device
II	I-Device
models	O
.	O
</s>
<s>
It	O
would	O
later	O
also	O
work	O
directly	O
with	O
the	O
built-in	O
disk	B-Device
port	O
on	O
the	O
Apple	B-Device
IIc	I-Device
Plus	I-Device
and	O
Apple	B-Device
IIGS	I-Device
through	O
backwards	O
compatibility	O
.	O
</s>
<s>
It	O
continued	O
to	O
be	O
sold	O
for	O
use	O
with	O
the	O
Apple	O
IIc	O
and	O
IIe	O
which	O
could	O
not	O
use	O
the	O
subsequent	O
replacement	O
Apple	O
-inch	O
drive	O
,	O
until	O
the	O
Apple	B-Device
IIc	I-Device
Plus	I-Device
redesign	O
in	O
1988	O
and	O
Apple	B-Device
II	I-Device
3.5	O
Disk	B-General_Concept
Controller	I-General_Concept
Card	O
released	O
in	O
1991	O
.	O
</s>
<s>
The	O
-inch	O
format	O
was	O
not	O
very	O
popular	O
in	O
the	O
Apple	B-Device
II	I-Device
community	O
(	O
excluding	O
the	O
16-bit	O
Apple	B-Device
IIGS	I-Device
)	O
as	O
most	O
software	O
was	O
released	O
in	O
the	O
5.25-inch	O
format	O
to	O
accommodate	O
the	O
existing	O
installed	O
Disk	B-Device
II	I-Device
drives	O
.	O
</s>
<s>
In	O
January	O
1986	O
,	O
Apple	O
introduced	O
the	O
Macintosh	B-Device
Plus	I-Device
which	O
had	O
a	O
Sony	O
double-sided	O
800-kilobyte	O
capacity	O
disk	B-Device
drive	I-Device
,	O
and	O
used	O
the	O
new	O
HFS	B-Application
disk	B-Device
format	O
providing	O
directories	O
and	O
sub-directories	O
.	O
</s>
<s>
This	O
drive	O
was	O
fitted	O
into	O
an	O
external	O
case	O
as	O
the	O
Macintosh	B-Device
800K	O
External	O
Drive	O
(	O
M0131	O
)	O
,	O
which	O
was	O
slimmer	O
than	O
the	O
earlier	O
400-kilobyte	O
drive	O
.	O
</s>
<s>
It	O
could	O
be	O
used	O
with	O
Macintosh	B-Device
models	O
except	O
for	O
the	O
original	O
128K	O
,	O
which	O
could	O
not	O
load	O
the	O
HFS	B-Application
disk	B-Device
format	O
.	O
</s>
<s>
The	O
drive	O
supported	O
the	O
older	O
400-kilobyte	O
single-sided	O
disks	B-Device
allowing	O
them	O
to	O
be	O
shared	O
.	O
</s>
<s>
The	O
use	O
of	O
Apple	O
's	O
GCR	B-Device
with	O
variable	O
speed	O
(	O
as	O
used	O
on	O
the	O
400-kilobyte	O
drive	O
)	O
accommodated	O
a	O
higher	O
storage	O
capacity	O
than	O
its	O
720-kilobyte	O
PC	O
counterparts	O
.	O
</s>
<s>
Designed	O
primarily	O
to	O
run	O
on	O
Macs	O
with	O
the	O
new	O
128-kilobyte	O
ROM	B-Device
which	O
contained	O
the	O
necessary	O
code	O
to	O
support	O
the	O
drive	O
,	O
it	O
could	O
be	O
used	O
with	O
Macs	O
with	O
older	O
64-kilobyte	O
ROMs	O
if	O
the	O
proper	O
software	O
was	O
loaded	O
from	O
the	O
system	B-Application
folder	O
of	O
a	O
Hard	B-Device
Disk	I-Device
20	I-Device
into	O
the	O
Mac	O
's	O
RAM	B-Architecture
.	O
</s>
<s>
The	O
drive	O
controlled	O
its	O
own	O
speed	O
and	O
was	O
no	O
longer	O
dependent	O
on	O
an	O
external	O
signal	O
from	O
the	O
Mac	O
,	O
which	O
was	O
blocked	O
on	O
the	O
early	O
drive	O
mechanisms	O
compatible	O
only	O
with	O
the	O
Macintosh	B-Device
.	O
</s>
<s>
Later	O
universal	O
mechanisms	O
,	O
first	O
used	O
on	O
the	O
Apple	B-Device
II	I-Device
to	O
accommodate	O
proprietary	O
signals	O
,	O
required	O
special	O
cables	O
to	O
isolate	O
the	O
speed	O
signal	O
from	O
the	O
Mac	O
,	O
to	O
prevent	O
damage	O
to	O
the	O
drive	O
.	O
</s>
<s>
However	O
,	O
with	O
its	O
increased	O
storage	O
capacity	O
combined	O
with	O
2-4	O
times	O
the	O
RAM	B-Architecture
available	O
on	O
the	O
Mac	B-Device
Plus	I-Device
,	O
the	O
external	O
drive	O
was	O
less	O
of	O
a	O
necessity	O
than	O
it	O
had	O
been	O
with	O
its	O
predecessors	O
.	O
</s>
<s>
Nevertheless	O
,	O
with	O
the	O
only	O
option	O
for	O
adding	O
additional	O
storage	O
being	O
extremely	O
expensive	O
hard	O
drives	O
,	O
a	O
year	O
later	O
Apple	O
increased	O
the	O
maximum	O
number	O
of	O
floppy	B-Device
drives	I-Device
that	O
could	O
be	O
accessed	O
simultaneously	O
to	O
three	O
on	O
the	O
Macintosh	B-Device
SE	I-Device
(	O
the	O
Macintosh	B-Device
Portable	I-Device
was	O
the	O
only	O
other	O
Mac	O
to	O
do	O
so	O
)	O
.	O
</s>
<s>
The	O
Apple	O
3.5	O
Drive	O
(	O
A9M0106	O
)	O
is	O
an	O
800K	O
external	O
drive	O
released	O
in	O
conjunction	O
with	O
the	O
Apple	B-Device
IIGS	I-Device
computer	O
and	O
replaced	O
the	O
beige-colored	O
Macintosh	B-Device
800K	O
External	O
Drive	O
.	O
</s>
<s>
It	O
works	O
on	O
both	O
the	O
Apple	B-Device
IIGS	I-Device
as	O
well	O
as	O
the	O
Macintosh	B-Device
.	O
</s>
<s>
Like	O
the	O
UniDisk	O
3.5	O
,	O
the	O
Apple	O
3.5	O
Drive	O
includes	O
Apple	O
II-specific	O
features	O
such	O
as	O
a	O
manual	O
disk	B-Device
eject	O
button	O
and	O
a	O
daisy-chain	O
connector	O
which	O
allows	O
two	O
drives	O
to	O
be	O
connected	O
to	O
an	O
Apple	B-Device
II	I-Device
computer	O
.	O
</s>
<s>
The	O
Macintosh	B-Device
however	O
could	O
still	O
only	O
accommodate	O
one	O
external	O
drive	O
,	O
and	O
ignores	O
use	O
of	O
the	O
eject	O
button	O
.	O
</s>
<s>
Unlike	O
the	O
Macintosh	B-Device
800K	O
External	O
Drive	O
,	O
the	O
Apple	O
3.5	O
Drive	O
can	O
be	O
used	O
natively	O
with	O
the	O
64-kilobyte	O
ROM	B-Device
stock	O
Macintosh	B-Device
128K	I-Device
&	O
512K	O
computers	O
without	O
the	O
HD20	O
INIT	O
,	O
albeit	O
only	O
with	O
400K	O
MFS	B-Application
formatted	O
disks	B-Device
.	O
</s>
<s>
Designed	O
as	O
a	O
universal	O
external	O
drive	O
replacement	O
,	O
the	O
Apple	O
3.5	O
Drive	O
was	O
eventually	O
made	O
compatible	O
with	O
the	O
remaining	O
Apple	B-Device
II	I-Device
models	O
in	O
production	O
upon	O
the	O
introduction	O
of	O
the	O
Apple	B-Device
IIc	I-Device
Plus	I-Device
and	O
the	O
Apple	B-Device
II	I-Device
3.5	O
Disk	B-General_Concept
Controller	I-General_Concept
Card	O
for	O
the	O
Apple	O
IIe	O
.	O
</s>
<s>
Following	O
the	O
success	O
of	O
the	O
Macintosh	B-Device
implementation	O
of	O
the	O
-inch	O
format	O
,	O
the	O
format	O
was	O
also	O
adopted	O
widely	O
by	O
the	O
personal	O
computer	O
industry	O
.	O
</s>
<s>
However	O
most	O
of	O
the	O
industry	O
adopted	O
a	O
different	O
Modified	B-Protocol
Frequency	I-Protocol
Modulation	I-Protocol
(	O
MFM	B-Protocol
)	O
formatting	O
scheme	O
at	O
a	O
fixed	O
rotational	O
speed	O
,	O
incompatible	O
with	O
Apple	O
's	O
own	O
GCR	B-Device
with	O
variable	O
speed	O
,	O
resulting	O
in	O
a	O
less-expensive	O
drive	O
,	O
but	O
with	O
a	O
lower	O
capacity	O
(	O
720KB	O
rather	O
than	O
800KB	O
)	O
.	O
</s>
<s>
In	O
1987	O
a	O
newer	O
and	O
better	O
,	O
MFM-based	O
,	O
"	O
high-density	O
"	O
format	O
was	O
developed	O
which	O
IBM	O
first	O
introduced	O
in	O
their	O
PS/2	B-Device
systems	O
,	O
doubling	O
the	O
previous	O
storage	O
capacity	O
to	O
1.4MB	O
.	O
</s>
<s>
In	O
Apple	O
's	O
pursuit	O
of	O
cross-compatibility	O
with	O
DOS	O
and	O
Windows-based	O
systems	O
to	O
attract	O
more	O
business	O
customers	O
,	O
they	O
adopted	O
the	O
new	O
format	O
,	O
thus	O
confirming	O
it	O
as	O
the	O
first	O
industry-wide	O
floppy	B-Device
disk	I-Device
standard	O
.	O
</s>
<s>
Later	O
renamed	O
the	O
Apple	O
SuperDrive	O
(	O
G7287	O
)	O
,	O
the	O
Apple	O
FDHD	O
Drive	O
(	O
Floppy	B-Device
Disk	I-Device
High	O
Density	O
)	O
was	O
introduced	O
in	O
1989	O
as	O
Apple	O
's	O
first	O
external	O
1.44MB	O
high-density	O
double-sided	O
-inch	O
floppy	B-Device
drive	I-Device
.	O
</s>
<s>
It	O
supported	O
all	O
of	O
Apple	O
's	O
3.5	B-Device
"	I-Device
floppy	I-Device
disk	I-Device
formats	O
as	O
well	O
as	O
all	O
standard	O
PC	O
formats	O
(	O
e.g.	O
</s>
<s>
MS-DOS	B-Application
,	O
Windows	B-Application
)	O
,	O
allowing	O
the	O
Macintosh	B-Device
to	O
read	O
and	O
write	O
all	O
industry-standard	O
floppy	B-Device
disk	I-Device
formats	O
.	O
</s>
<s>
The	O
external	O
drive	O
was	O
offered	O
only	O
briefly	O
with	O
support	O
for	O
the	O
Apple	B-Device
II	I-Device
,	O
coming	O
late	O
in	O
that	O
product	O
's	O
life	O
.	O
</s>
<s>
To	O
take	O
advantage	O
of	O
the	O
drive	O
's	O
extended	O
storage	O
and	O
new	O
capabilities	O
,	O
it	O
required	O
the	O
new	O
SWIM	B-General_Concept
(	O
Sander	O
–	O
Wozniak	O
Integrated	O
Machine	O
)	O
floppy	B-Device
disk	B-General_Concept
controller	I-General_Concept
chip	O
to	O
be	O
present	O
on	O
the	O
Macintosh	B-Device
and	O
Apple	B-Device
II	I-Device
,	O
the	O
latter	O
requiring	O
the	O
Apple	B-Device
II	I-Device
3.5	O
Disk	B-General_Concept
Controller	I-General_Concept
Card	O
which	O
integrated	O
the	O
chip	O
.	O
</s>
<s>
If	O
the	O
drive	O
was	O
connected	O
to	O
an	O
older	O
Macintosh	B-Device
,	O
Apple	B-Device
IIGS	I-Device
or	O
Apple	B-Device
IIc	I-Device
Plus	I-Device
with	O
the	O
older	O
IWM	B-Device
(	O
Integrated	B-Device
Woz	I-Device
Machine	I-Device
)	O
chip	O
,	O
the	O
drive	O
would	O
act	O
as	O
a	O
standard	O
800K	O
drive	O
,	O
without	O
any	O
additional	O
capabilities	O
.	O
</s>
<s>
The	O
interface	O
card	O
was	O
necessary	O
for	O
the	O
Apple	B-Device
IIGS	I-Device
to	O
make	O
use	O
of	O
its	O
greater	O
storage	O
capacity	O
and	O
ability	O
to	O
handle	O
PC	O
formats	O
.	O
</s>
<s>
The	O
last	O
Mac	O
it	O
could	O
be	O
used	O
with	O
was	O
the	O
Classic	B-Device
II	I-Device
and	O
was	O
discontinued	O
shortly	O
thereafter	O
.	O
</s>
<s>
The	O
drive	O
was	O
fitted	O
in	O
every	O
desktop	O
Mac	O
from	O
its	O
introduction	O
and	O
was	O
eliminated	O
with	O
the	O
introduction	O
of	O
the	O
iMac	B-Device
in	O
1998	O
.	O
</s>
<s>
Manufactured	O
exclusively	O
for	O
use	O
with	O
the	O
Macintosh	B-Device
PowerBook	O
line	O
,	O
the	O
Macintosh	B-Device
HDI-20	O
External	O
1.44MB	O
Floppy	B-Device
Disk	I-Device
Drive	I-Device
(	O
M8061	O
)	O
contained	O
a	O
low-powered	O
,	O
slimmer	O
version	O
of	O
the	O
SuperDrive	O
and	O
used	O
a	O
small	O
square	O
HDI-20	O
proprietary	O
connector	O
,	O
rather	O
than	O
the	O
larger	O
standard	O
DE-19	O
desktop	O
connector	O
,	O
and	O
was	O
powered	O
directly	O
by	O
the	O
laptop	O
.	O
</s>
<s>
Compatible	O
only	O
with	O
the	O
PowerBook	B-Device
2400c	I-Device
,	O
the	O
Macintosh	B-Device
PowerBook	B-Device
2400c	I-Device
Floppy	B-Device
Disk	I-Device
Drive	I-Device
(	O
M4327	O
)	O
used	O
a	O
unique	O
Molex	O
connector	O
rather	O
than	O
the	O
previous	O
HDI-20	O
connector	O
.	O
</s>
<s>
Possibly	O
because	O
of	O
the	O
2400c	O
's	O
IBM	O
design	O
heritage	O
,	O
both	O
the	O
drive	O
and	O
the	O
computer	O
use	O
the	O
same	O
connectors	O
as	O
IBM	O
ThinkPad	O
external	O
floppy	B-Device
drives	I-Device
from	O
the	O
same	O
period	O
;	O
however	O
,	O
IBM	O
drives	O
are	O
not	O
electrically	O
compatible	O
.	O
</s>
<s>
The	O
drive	O
was	O
discontinued	O
in	O
1998	O
and	O
would	O
be	O
the	O
last	O
external	O
floppy	B-Device
drive	I-Device
manufactured	O
by	O
Apple	O
.	O
</s>
