<s>
It	O
went	O
on	O
sale	O
in	O
June	O
1978	O
at	O
a	O
retail	O
price	O
of	O
US$495	O
for	O
pre-order	O
;	O
it	O
was	O
later	O
sold	O
for	O
$595	O
(	O
)	O
including	O
the	O
controller	B-General_Concept
card	I-General_Concept
(	O
which	O
can	O
control	O
up	O
to	O
two	O
drives	O
)	O
and	O
cable	O
.	O
</s>
<s>
The	O
Disk	B-Device
II	I-Device
was	O
designed	O
specifically	O
for	O
use	O
with	O
the	O
Apple	B-Device
II	I-Device
personal	B-Device
computer	I-Device
family	O
to	O
replace	O
the	O
slower	O
cassette	O
tape	O
storage	O
.	O
</s>
<s>
These	O
floppy	B-Device
drives	I-Device
cannot	O
be	O
used	O
with	O
any	O
Macintosh	B-Device
without	O
an	O
Apple	B-Device
IIe	I-Device
Card	I-Device
as	O
doing	O
so	O
will	O
damage	O
the	O
drive	O
or	O
the	O
controller	O
.	O
</s>
<s>
Apple	O
produced	O
at	O
least	O
six	O
variants	O
of	O
the	O
basic	O
-inch	O
Disk	B-Device
II	I-Device
concept	O
over	O
the	O
course	O
of	O
the	O
Apple	B-Device
II	I-Device
series	O
 '	O
lifetime	O
:	O
The	O
Disk	B-Device
II	I-Device
,	O
the	O
Disk	O
III	O
,	O
the	O
DuoDisk	O
,	O
the	O
Disk	O
IIc	O
,	O
the	O
UniDisk	O
5.25	B-Device
"	I-Device
and	O
the	O
Apple	O
5.25	O
Drive	O
.	O
</s>
<s>
Most	O
DuoDisk	O
drives	O
,	O
the	O
Disk	O
IIc	O
,	O
the	O
UniDisk	O
5.25	B-Device
"	I-Device
and	O
the	O
AppleDisk	O
5.25	B-Device
"	I-Device
even	O
use	O
the	O
same	O
19-pin	O
D-Sub	B-Protocol
connector	I-Protocol
,	O
so	O
they	O
are	O
directly	O
interchangeable	O
.	O
</s>
<s>
The	O
only	O
"	O
drive	O
Apple	O
sold	O
aside	O
from	O
the	O
Disk	B-Device
II	I-Device
family	O
was	O
a	O
360k	B-Device
MFM	B-Protocol
unit	O
made	O
to	O
allow	O
Mac	B-Device
IIs	I-Device
and	O
SEs	O
to	O
read	O
PC	B-Device
floppy	I-Device
disks	I-Device
.	O
</s>
<s>
Apple	O
did	O
not	O
originally	O
offer	O
a	O
disk	O
drive	O
for	O
the	O
Apple	B-Device
II	I-Device
,	O
which	O
used	O
data	O
cassette	O
storage	O
like	O
other	O
microcomputers	O
of	O
the	O
time	O
.	O
</s>
<s>
Wozniak	O
knew	O
nothing	O
about	O
disk	B-General_Concept
controllers	I-General_Concept
,	O
but	O
while	O
at	O
Hewlett-Packard	O
he	O
had	O
designed	O
a	O
simple	O
,	O
five-chip	O
circuit	O
to	O
operate	O
a	O
Shugart	O
Associates	O
drive	O
.	O
</s>
<s>
The	O
Apple	B-Device
II	I-Device
's	O
lack	O
of	O
a	O
disk	O
drive	O
was	O
"	O
a	O
glaring	O
weakness	O
"	O
in	O
what	O
was	O
otherwise	O
intended	O
to	O
be	O
a	O
polished	O
,	O
professional	O
product	O
.	O
</s>
<s>
Speaking	O
later	O
,	O
Osborne	B-Device
1	I-Device
designer	O
Lee	O
Felsenstein	O
stated	O
,	O
"	O
The	O
difference	O
between	O
cassette	O
and	O
disk	O
systems	O
was	O
the	O
difference	O
between	O
hobbyist	O
devices	O
and	O
a	O
computer	O
.	O
</s>
<s>
You	O
could	O
n't	O
have	O
expected	O
,	O
say	O
,	O
VisiCalc	B-Application
,	O
to	O
run	O
on	O
a	O
cassette	O
system.	O
"	O
</s>
<s>
Recognizing	O
that	O
the	O
II	O
needed	O
a	O
disk	O
drive	O
to	O
be	O
taken	O
seriously	O
,	O
Apple	O
set	O
out	O
to	O
develop	O
a	O
disk	O
drive	O
and	O
a	O
DOS	B-Application
to	O
run	O
it	O
.	O
</s>
<s>
Still	O
lacking	O
a	O
DOS	B-Application
,	O
and	O
with	O
Wozniak	O
inexperienced	O
in	O
operating	O
system	O
design	O
,	O
Steve	O
Jobs	O
approached	O
Shepardson	O
Microsystems	O
with	O
the	O
project	O
.	O
</s>
<s>
On	O
April	O
10	O
,	O
1978	O
Apple	O
signed	O
a	O
contract	O
for	O
$	O
13,000	O
with	O
Shepardson	O
to	O
develop	O
the	O
DOS	B-Application
.	O
</s>
<s>
After	O
Wozniak	O
finished	O
studying	O
IBM	O
disk	B-General_Concept
controller	I-General_Concept
designs	O
,	O
Jobs	O
then	O
demanded	O
that	O
Shugart	O
sell	O
them	O
a	O
stripped	O
disk	O
drive	O
that	O
had	O
no	O
controller	O
board	O
,	O
index	O
sensor	O
,	O
load	O
solenoids	O
,	O
or	O
track	O
zero	O
sensor	O
.	O
</s>
<s>
Although	O
puzzled	O
by	O
this	O
request	O
,	O
Shugart	O
complied	O
and	O
provided	O
Apple	O
with	O
25	O
drive	O
mechanisms	O
that	O
they	O
could	O
use	O
as	O
prototypes	O
in	O
developing	O
a	O
disk	O
system	O
for	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
Wozniak	O
studied	O
North	O
Star	O
Computers	O
and	O
others	O
 '	O
more	O
complex	O
floppy	B-Device
controllers	O
.	O
</s>
<s>
Following	O
the	O
Shugart	O
controller	O
's	O
manual	O
,	O
Wozniak	O
attempted	O
to	O
develop	O
an	O
FM-type	O
controller	O
with	O
10	O
sector	O
per	O
track	O
storage	O
,	O
but	O
realized	O
that	O
Group	B-Device
Coded	I-Device
Recording	I-Device
could	O
fit	O
13	O
sectors	O
per	O
track	O
.	O
</s>
<s>
Wozniak	O
called	O
the	O
resultant	O
Disk	B-Device
II	I-Device
system	O
"	O
my	O
most	O
incredible	O
experience	O
at	O
Apple	O
and	O
the	O
finest	O
job	O
I	O
did	O
"	O
,	O
and	O
credited	O
it	O
and	O
VisiCalc	B-Application
with	O
the	O
Apple	B-Device
II	I-Device
's	O
success	O
.	O
</s>
<s>
The	O
Disk	B-Device
II	I-Device
was	O
very	O
successful	O
for	O
Apple	O
,	O
being	O
the	O
cheapest	O
floppy	B-Device
disk	I-Device
system	O
ever	O
sold	O
up	O
to	O
that	O
point	O
and	O
immensely	O
profitable	O
for	O
the	O
company	O
,	O
in	O
addition	O
to	O
having	O
nearly	O
20%	O
more	O
storage	O
space	O
than	O
standard	O
FM	B-Protocol
drives	O
.	O
</s>
<s>
For	O
a	O
while	O
,	O
the	O
only	O
direct	O
competitor	O
in	O
the	O
microcomputer	O
industry	O
was	O
the	O
TRS-80	B-Device
Model	I-Device
I	I-Device
,	O
which	O
had	O
used	O
only	O
standard	O
FM	B-Protocol
storage	O
for	O
85k	O
.	O
</s>
<s>
Both	O
the	O
Atari	B-Device
8-bit	I-Device
and	O
Commodore	O
64	O
's	O
disk	O
drives	O
 '	O
throughputs	O
were	O
much	O
slower	O
than	O
the	O
Disk	B-Device
II	I-Device
's	O
15KB/s	O
,	O
seriously	O
affecting	O
their	O
ability	O
to	O
compete	O
in	O
the	O
business	O
market	O
.	O
</s>
<s>
However	O
,	O
the	O
advantage	O
of	O
Wozniak	O
's	O
design	O
was	O
somewhat	O
nullified	O
when	O
the	O
cost	O
of	O
double-density	O
MFM	B-Protocol
controllers	O
dropped	O
only	O
a	O
year	O
after	O
the	O
Disk	B-Device
II	I-Device
's	O
introduction	O
.	O
</s>
<s>
The	O
initial	O
Disk	B-Device
II	I-Device
drives	O
(	O
A2M0003	O
)	O
were	O
modifications	O
of	O
the	O
Shugart	O
SA-400	O
,	O
which	O
was	O
the	O
first	O
commercially	O
available	O
-inch	O
diskette	B-Device
drive	O
.	O
</s>
<s>
Normal	O
storage	O
capacity	O
per	O
disk	O
side	O
was	O
113.75KB	O
with	O
Apple	B-Operating_System
DOS	I-Operating_System
3.2.1	O
and	O
earlier	O
(	O
256	O
bytes	O
per	O
sector	O
,	O
13	O
sectors	O
per	O
track	O
,	O
35	O
tracks	O
per	O
side	O
)	O
,	O
or	O
140KB	O
with	O
DOS	B-Application
3.3	O
and	O
ProDOS	O
(	O
256	O
bytes	O
per	O
sector	O
,	O
16	O
sectors	O
per	O
track	O
,	O
35	O
tracks	O
per	O
side	O
)	O
.	O
</s>
<s>
The	O
16-sector	O
hardware	O
upgrade	O
introduced	O
in	O
1980	O
for	O
use	O
with	O
DOS	B-Application
3.3	O
modified	O
only	O
the	O
controller	B-General_Concept
card	I-General_Concept
firmware	O
to	O
use	O
a	O
more	O
efficient	O
GCR	B-Device
code	O
called	O
"	O
6	O
and	O
2	O
encoding	O
"	O
.	O
</s>
<s>
This	O
update	O
had	O
the	O
disadvantage	O
of	O
not	O
automatically	O
booting	O
older	O
13	O
sector	O
Apple	B-Device
II	I-Device
software	O
.	O
</s>
<s>
Since	O
the	O
Disk	B-Device
II	I-Device
controller	O
was	O
completely	O
software-operated	O
,	O
the	O
user	O
had	O
total	O
control	O
over	O
the	O
encoding	O
and	O
format	O
so	O
long	O
as	O
it	O
was	O
within	O
the	O
physical	O
limits	O
of	O
the	O
drive	O
mechanism	O
and	O
media	O
.	O
</s>
<s>
This	O
also	O
allowed	O
software	O
companies	O
to	O
use	O
all	O
sorts	O
of	O
ingenious	O
copy	B-Application
protection	I-Application
schemes	O
.	O
</s>
<s>
The	O
Shugart	O
SA-400	O
,	O
from	O
which	O
the	O
Disk	B-Device
II	I-Device
was	O
adapted	O
,	O
was	O
a	O
single-sided	O
,	O
35-track	O
drive	O
.	O
</s>
<s>
However	O
,	O
it	O
was	O
common	O
for	O
users	O
to	O
manually	O
flip	O
the	O
disk	O
to	O
utilize	O
the	O
opposite	O
side	O
,	O
after	O
cutting	O
a	O
second	O
notch	O
on	O
the	O
diskette	B-Device
's	O
protective	O
shell	O
to	O
allow	O
write-access	O
.	O
</s>
<s>
Only	O
one	O
side	O
could	O
be	O
accessed	O
at	O
once	O
,	O
but	O
it	O
did	O
essentially	O
double	O
the	O
capacity	O
of	O
each	O
floppy	B-Device
diskette	I-Device
,	O
an	O
important	O
consideration	O
especially	O
in	O
the	O
early	O
years	O
when	O
media	O
was	O
still	O
quite	O
expensive	O
.	O
</s>
<s>
In	O
the	O
Disk	B-Device
II	I-Device
,	O
the	O
full-height	B-Device
drive	I-Device
mechanism	O
shipped	O
inside	O
a	O
beige-painted	O
metal	O
case	O
and	O
connected	O
to	O
the	O
controller	B-General_Concept
card	I-General_Concept
via	O
a	O
20-pin	O
ribbon	O
cable	O
;	O
the	O
controller	B-General_Concept
card	I-General_Concept
was	O
plugged	O
into	O
one	O
of	O
the	O
bus	O
slots	O
on	O
the	O
Apple	O
's	O
mainboard	O
.	O
</s>
<s>
The	O
connector	O
is	O
very	O
easy	O
to	O
misalign	O
on	O
the	O
controller	B-General_Concept
card	I-General_Concept
,	O
which	O
will	O
short	O
out	O
a	O
certain	O
IC	O
in	O
the	O
drive	O
;	O
if	O
later	O
connected	O
correctly	O
,	O
a	O
drive	O
damaged	O
this	O
way	O
will	O
delete	O
data	O
from	O
any	O
disk	O
inserted	O
into	O
it	O
as	O
soon	O
as	O
it	O
starts	O
spinning	O
,	O
even	O
write-protected	O
disks	O
such	O
as	O
those	O
used	O
to	O
distribute	O
commercial	O
software	O
.	O
</s>
<s>
DB-19	B-Protocol
adapters	O
for	O
the	O
original	O
Disk	B-Device
II	I-Device
were	O
eventually	O
available	O
for	O
use	O
with	O
Apple	O
's	O
later	O
connector	O
standard	O
.	O
</s>
<s>
Up	O
to	O
14	O
drives	O
could	O
be	O
attached	O
to	O
one	O
Apple	B-Device
II	I-Device
or	O
Apple	B-Device
IIe	I-Device
computer	O
-	O
two	O
drives	O
per	O
controller	B-General_Concept
card	I-General_Concept
,	O
one	O
card	O
per	O
slot	O
,	O
and	O
there	O
were	O
seven	O
usable	O
slots	O
per	O
computer	O
.	O
</s>
<s>
While	O
the	O
DOS	B-Application
and	O
ProDOS	O
operating	O
systems	O
worked	O
equally	O
well	O
with	O
the	O
card	O
in	O
any	O
of	O
the	O
normal	O
slots	O
(	O
i.e.	O
</s>
<s>
all	O
except	O
slot	O
0	O
of	O
the	O
Apple	O
II/II	O
+	O
or	O
the	O
special	O
memory	O
expansion	O
slots	O
of	O
the	O
later	O
models	O
)	O
,	O
Apple	O
's	O
printed	O
manuals	O
suggested	O
using	O
slot	O
6	O
for	O
the	O
first	O
controller	B-General_Concept
card	I-General_Concept
;	O
most	O
Apple	B-Device
II	I-Device
software	O
expects	O
this	O
slot	O
to	O
be	O
used	O
for	O
the	O
main	O
-inch	O
disk	O
drive	O
and	O
fails	O
otherwise	O
.	O
</s>
<s>
A	O
Bell	O
&	O
Howell	O
version	O
of	O
the	O
Disk	B-Device
II	I-Device
was	O
also	O
manufactured	O
by	O
Apple	O
in	O
a	O
black	O
painted	O
case	O
,	O
which	O
matched	O
the	O
color	O
of	O
the	O
Bell	O
&	O
Howell	O
version	O
of	O
the	O
Apple	B-Device
II	I-Device
Plus	O
,	O
which	O
Apple	O
was	O
already	O
manufacturing	O
.	O
</s>
<s>
In	O
1978	O
,	O
Apple	O
intended	O
to	O
develop	O
its	O
own	O
"	O
FileWare	B-Device
"	O
drive	O
mechanism	O
for	O
use	O
in	O
the	O
new	O
Apple	B-Device
///	I-Device
and	O
Lisa	B-Device
business	O
computers	O
then	O
being	O
developed	O
.	O
</s>
<s>
They	O
quickly	O
ran	O
into	O
difficulties	O
with	O
the	O
mechanisms	O
,	O
which	O
precluded	O
them	O
from	O
being	O
incorporated	O
in	O
the	O
Apple	B-Device
///	I-Device
.	O
</s>
<s>
That	O
machine	O
thus	O
continued	O
to	O
use	O
the	O
same	O
Shugart	O
design	O
as	O
the	O
Disk	B-Device
II	I-Device
.	O
</s>
<s>
The	O
first	O
variation	O
of	O
the	O
Disk	B-Device
II	I-Device
introduced	O
for	O
the	O
Apple	B-Device
///	I-Device
,	O
called	O
the	O
Disk	O
III	O
(	O
A3M0004	O
)	O
,	O
used	O
the	O
identical	O
drive	O
mechanism	O
inside	O
a	O
modified	O
plastic	O
case	O
with	O
a	O
proprietary	O
connector	O
.	O
</s>
<s>
Though	O
Apple	O
sought	O
to	O
force	O
the	O
purchase	O
of	O
new	O
drives	O
with	O
the	O
Apple	B-Device
///	I-Device
,	O
many	O
former	O
Apple	B-Device
II	I-Device
users	O
quickly	O
devised	O
a	O
way	O
to	O
adapt	O
their	O
existing	O
and	O
cheaper	O
Disk	B-Device
II	I-Device
drives	O
;	O
however	O
,	O
only	O
one	O
external	O
Disk	B-Device
II	I-Device
was	O
supported	O
in	O
this	O
manner	O
.	O
</s>
<s>
The	O
Disk	O
III	O
was	O
the	O
first	O
to	O
allow	O
daisy	O
chaining	O
of	O
up	O
to	O
three	O
additional	O
drives	O
to	O
the	O
single	O
26-pin	O
ribbon	O
cable	O
connector	O
on	O
the	O
Apple	B-Device
///	I-Device
,	O
for	O
a	O
total	O
of	O
4	O
floppy	B-Device
disk	I-Device
drives	I-Device
–	O
the	O
Apple	B-Device
///	I-Device
was	O
the	O
first	O
Apple	O
to	O
contain	O
a	O
built-in	O
drive	O
mechanism	O
.	O
</s>
<s>
The	O
Apple	B-Device
III	I-Device
Plus	O
changed	O
its	O
26-pin	O
connector	O
to	O
a	O
DB-25	B-Protocol
connector	I-Protocol
,	O
which	O
required	O
an	O
adapter	O
for	O
use	O
with	O
the	O
Disk	O
III	O
.	O
</s>
<s>
In	O
1983	O
,	O
Apple	O
finally	O
announced	O
a	O
single	O
and	O
dual	O
external	O
drive	O
(	O
UniFile	B-Device
and	O
DuoFile	B-Device
)	O
implementing	O
the	O
871-kilobyte	O
"	O
FileWare	B-Device
"	O
mechanism	O
used	O
in	O
the	O
original	O
Apple	B-Device
Lisa	I-Device
,	O
as	O
a	O
replacement	O
for	O
the	O
Disk	B-Device
II	I-Device
&	O
///	O
drives	O
.	O
</s>
<s>
In	O
1984	O
,	O
shortly	O
after	O
the	O
introduction	O
of	O
the	O
Apple	B-Device
IIe	I-Device
the	O
previous	O
year	O
,	O
Apple	O
offered	O
a	O
combination	O
of	O
two	O
,	O
two	B-Device
third-height	I-Device
,	O
140-kilobyte	O
Disk	B-Device
II	I-Device
drive	O
mechanisms	O
side-by-side	O
in	O
a	O
single	O
plastic	O
case	O
,	O
called	O
the	O
DuoDisk	O
(	O
A9M0108	O
)	O
,	O
which	O
could	O
not	O
be	O
daisy-chained	O
.	O
</s>
<s>
Each	O
unit	O
required	O
its	O
own	O
disk	B-General_Concept
controller	I-General_Concept
card	O
(	O
as	O
each	O
card	O
could	O
still	O
control	O
only	O
two	O
drives	O
)	O
and	O
the	O
number	O
of	O
units	O
was	O
thus	O
limited	O
to	O
the	O
number	O
of	O
available	O
slots	O
;	O
in	O
practice	O
,	O
few	O
uses	O
of	O
the	O
Apple	B-Device
II	I-Device
computer	O
can	O
make	O
good	O
use	O
of	O
more	O
than	O
two	O
-inch	O
drives	O
,	O
so	O
this	O
limitation	O
mattered	O
little	O
.	O
</s>
<s>
Originally	O
released	O
with	O
a	O
DB-25	B-Protocol
connector	I-Protocol
to	O
match	O
that	O
of	O
the	O
Apple	B-Device
III	I-Device
Plus	O
,	O
it	O
was	O
the	O
first	O
to	O
adopt	O
Apple	O
's	O
standard	O
DB-19	B-Protocol
floppy	B-Device
drive	I-Device
connector	O
.	O
</s>
<s>
The	O
Disk	O
IIc	O
(	O
A2M4050	O
)	O
was	O
a	O
half-height	B-Device
-inch	O
floppy	B-Device
disk	I-Device
drive	I-Device
introduced	O
by	O
Apple	O
Computer	O
in	O
1984	O
styled	O
for	O
use	O
alongside	O
the	O
Apple	O
IIc	O
personal	B-Device
computer	I-Device
,	O
the	O
only	O
Apple	B-Device
II	I-Device
to	O
contain	O
a	O
-inch	O
built-in	O
disk	O
drive	O
mechanism	O
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
use	O
it	O
on	O
other	O
Apple	B-Device
II	I-Device
models	O
,	O
so	O
long	O
as	O
it	O
came	O
last	O
in	O
the	O
chain	O
of	O
drive	O
devices	O
(	O
due	O
to	O
lacking	O
a	O
daisy-chain	O
port	O
)	O
;	O
but	O
since	O
the	O
Disk	O
IIc	O
was	O
sold	O
without	O
a	O
controller	B-General_Concept
card	I-General_Concept
,	O
the	O
Apple	O
IIc	O
computer	O
needing	O
none	O
,	O
it	O
had	O
to	O
be	O
adapted	O
to	O
an	O
existing	O
Disk	B-Device
II	I-Device
controller	B-General_Concept
card	I-General_Concept
in	O
this	O
case	O
.	O
</s>
<s>
Essentially	O
the	O
same	O
as	O
the	O
full-height	B-Device
Disk	B-Device
II	I-Device
,	O
Apple	O
sold	O
the	O
Disk	O
IIc	O
for	O
US$329	O
,	O
and	O
other	O
companies	O
later	O
sold	O
similar	O
drives	O
for	O
less	O
.	O
</s>
<s>
After	O
the	O
release	O
of	O
the	O
UniDisk	O
3.5	O
a	O
few	O
months	O
later	O
,	O
the	O
UniDisk	O
was	O
often	O
informally	O
referred	O
to	O
as	O
the	O
"	O
UniDisk	O
5.25	B-Device
"	I-Device
to	O
distinguish	O
the	O
similarly-named	O
drives	O
.	O
</s>
<s>
Since	O
the	O
UniDisk	O
could	O
fully	O
replace	O
the	O
Disk	B-Device
II	I-Device
in	O
all	O
its	O
uses	O
,	O
the	O
original	O
Disk	B-Device
II	I-Device
was	O
discontinued	O
at	O
this	O
point	O
.	O
</s>
<s>
In	O
1986	O
a	O
Platinum-gray	O
version	O
of	O
the	O
drive	O
named	O
the	O
Apple	O
5.25	O
Drive	O
(	O
A9M0107	O
)	O
was	O
introduced	O
alongside	O
the	O
first	O
Platinum-colored	O
computer	O
,	O
the	O
Apple	B-Device
IIGS	I-Device
.	O
</s>
<s>
The	O
drive	O
's	O
name	O
was	O
similar	O
to	O
that	O
of	O
the	O
Apple	O
3.5	O
Drive	O
,	O
also	O
released	O
with	O
the	O
IIGS	B-Device
.	O
</s>
<s>
Like	O
the	O
DuoDisk	O
and	O
Disk	O
IIc	O
before	O
them	O
,	O
the	O
UniDisk	O
and	O
Apple	O
5.25	O
Drive	O
were	O
half-height	B-Device
disk	O
mechanisms	O
inside	O
an	O
individual	O
drive	O
enclosure	O
.	O
</s>
<s>
Both	O
drives	O
featured	O
a	O
daisy	B-Application
chain	I-Application
pass-through	O
port	O
.	O
</s>
<s>
While	O
the	O
drives	O
were	O
essentially	O
interchangeable	O
among	O
Apple	B-Device
II	I-Device
computers	O
,	O
both	O
with	O
each	O
other	O
and	O
with	O
the	O
earlier	O
drives	O
,	O
minor	O
electrical	O
differences	O
dictated	O
that	O
only	O
the	O
Apple	O
5.25	O
Drive	O
could	O
be	O
used	O
with	O
the	O
later	O
(	O
ROM	O
3	O
)	O
version	O
of	O
the	O
Apple	B-Device
IIGS	I-Device
and	O
with	O
the	O
Apple	B-Device
IIe	I-Device
Card	I-Device
on	O
a	O
Macintosh	B-Device
LC	I-Device
.	O
</s>
<s>
In	O
1984	O
,	O
Apple	O
had	O
opted	O
for	O
the	O
more	O
modern	O
,	O
Sony-designed	O
-inch	O
floppy	B-Device
disk	I-Device
in	O
late-model	O
Lisas	B-Device
and	O
the	O
new	O
Apple	B-Device
Macintosh	I-Device
.	O
</s>
<s>
Accordingly	O
,	O
they	O
attempted	O
to	O
introduce	O
a	O
new	O
-inch	O
800-kilobyte	O
floppy	B-Device
disk	I-Device
format	O
for	O
the	O
Apple	B-Device
II	I-Device
series	O
as	O
well	O
,	O
to	O
eventually	O
replace	O
the	O
140-kilobyte	O
Disk	B-Device
II	I-Device
format	O
.	O
</s>
<s>
However	O
,	O
the	O
external	O
UniDisk	O
3.5	O
drive	O
required	O
a	O
ROM	O
upgrade	O
(	O
for	O
existing	O
Apple	O
IIc	O
machines	O
;	O
new	O
ones	O
shipped	O
after	O
this	O
time	O
had	O
it	O
from	O
the	O
factory	O
)	O
or	O
a	O
new	O
kind	O
of	O
disk	B-General_Concept
controller	I-General_Concept
card	O
(	O
the	O
so-called	O
"	O
Liron	O
Card	O
"	O
,	O
for	O
the	O
Apple	B-Device
IIe	I-Device
)	O
to	O
be	O
used	O
.	O
</s>
<s>
The	O
much	O
larger	O
capacity	O
and	O
higher	O
bitrate	O
of	O
the	O
-inch	O
drives	O
made	O
it	O
impractical	O
to	O
use	O
the	O
software-driven	O
Disk	B-Device
II	I-Device
controller	O
because	O
the	O
1-megahertz	O
6502	B-General_Concept
CPU	O
in	O
the	O
Apple	B-Device
II	I-Device
line	O
was	O
too	O
slow	O
to	O
be	O
able	O
to	O
read	O
them	O
.	O
</s>
<s>
Thus	O
,	O
a	O
new	O
and	O
much	O
more	O
advanced	O
(	O
and	O
correspondingly	O
expensive	O
)	O
hardware	O
floppy	B-Device
controller	O
had	O
to	O
be	O
used	O
.	O
</s>
<s>
And	O
many	O
original	O
Apple	B-Device
IIs	I-Device
could	O
not	O
use	O
the	O
new	O
controller	B-General_Concept
card	I-General_Concept
at	O
all	O
without	O
further	O
upgrades	O
.	O
</s>
<s>
Also	O
,	O
almost	O
all	O
commercial	O
software	O
for	O
the	O
Apple	B-Device
II	I-Device
series	O
continued	O
to	O
be	O
published	O
on	O
-inch	O
disks	O
which	O
had	O
a	O
much	O
larger	O
installed	O
base	O
.	O
</s>
<s>
For	O
these	O
reasons	O
the	O
-inch	O
format	O
was	O
not	O
widely	O
accepted	O
by	O
Apple	B-Device
II	I-Device
users	O
.	O
</s>
<s>
The	O
Apple	O
3.5	O
Drive	O
used	O
the	O
same	O
800-kilobyte	O
format	O
as	O
the	O
UniDisk	O
3.5	B-Device
"	I-Device
,	O
but	O
it	O
did	O
away	O
with	O
the	O
internal	O
controller	O
,	O
which	O
made	O
it	O
cheaper	O
.	O
</s>
<s>
Unlike	O
all	O
earlier	O
Apple	B-Device
II	I-Device
drives	O
,	O
it	O
was	O
designed	O
to	O
work	O
with	O
the	O
Macintosh	B-Device
too	O
,	O
and	O
among	O
Apple	B-Device
II	I-Device
models	O
,	O
it	O
was	O
compatible	O
only	O
with	O
the	O
Apple	B-Device
IIGS	I-Device
and	O
the	O
Apple	B-Device
IIc+	I-Device
models	O
,	O
which	O
both	O
had	O
a	O
faster	O
main	O
CPU	O
.	O
</s>
<s>
On	O
the	O
Apple	B-Device
IIGS	I-Device
,	O
whose	O
improved	O
audiovisual	O
capacities	O
really	O
demanded	O
a	O
higher-capacity	O
disk	O
format	O
as	O
well	O
,	O
the	O
-inch	O
format	O
was	O
accepted	O
by	O
users	O
and	O
became	O
the	O
standard	O
format	O
.	O
</s>
<s>
Though	O
Apple	O
eventually	O
offered	O
a	O
1.44-megabyte	O
SuperDrive	B-Device
with	O
matching	O
controller	B-General_Concept
card	I-General_Concept
for	O
the	O
Apple	B-Device
II	I-Device
series	O
as	O
well	O
,	O
the	O
-inch	O
Disk	B-Device
II	I-Device
format	O
drives	O
continued	O
to	O
be	O
offered	O
alongside	O
the	O
newer	O
-inch	O
drives	O
and	O
remained	O
the	O
standard	O
on	O
the	O
non-IIGS	O
models	O
until	O
the	O
platform	O
was	O
discontinued	O
in	O
1993	O
.	O
</s>
<s>
Officially	O
,	O
the	O
following	O
-inch	O
drives	O
could	O
be	O
used	O
on	O
the	O
Apple	B-Device
II	I-Device
:	O
</s>
<s>
Apple	O
3.5	O
"	O
External	O
(	O
A9M0106	O
)	O
–	O
Designed	O
for	O
Apple	B-Device
IIs	I-Device
with	O
the	O
Liron	O
or	O
Superdrive	B-Device
controller	O
or	O
all	O
Macintoshes	B-Device
with	O
an	O
external	O
19-pin	O
floppy	B-Device
port	O
(	O
Mac	O
512s	O
must	O
be	O
booted	O
from	O
the	O
internal	O
400-kilobyte	O
drive	O
with	O
the	O
HD20	O
INIT	O
,	O
which	O
provides	O
HFS	O
file	O
system	O
support	O
–	O
the	O
Macintosh	B-Device
128K	I-Device
will	O
not	O
work	O
with	O
this	O
)	O
.	O
</s>
<s>
The	O
drive	O
can	O
be	O
daisy	O
chained	O
,	O
however	O
this	O
feature	O
is	O
not	O
supported	O
on	O
the	O
Macintosh	B-Device
.	O
</s>
<s>
Apple	O
FDHD	B-Device
External	O
(	O
G7287	O
)	O
–	O
Supports	O
720-kilobyte/1.44	O
-megabyte	O
MFM	B-Protocol
floppy	B-Device
disks	I-Device
in	O
addition	O
to	O
800-kilobyte	O
GCR	B-Device
.	O
</s>
<s>
The	O
400-kilobyte	O
and	O
800-kilobyte	O
Macintosh	B-Device
external	O
drives	O
(	O
M0130	O
and	O
M0131	O
)	O
are	O
incompatible	O
with	O
standard	O
Apple	B-Device
II	I-Device
controllers	O
as	O
they	O
do	O
not	O
support	O
the	O
drives	O
 '	O
automatic	O
disk-eject	O
feature	O
,	O
although	O
they	O
could	O
be	O
used	O
with	O
third-party	O
controllers	O
.	O
</s>
<s>
Alongside	O
the	O
release	O
of	O
the	O
Macintosh	B-Device
SE	I-Device
&	O
Macintosh	B-Device
II	I-Device
,	O
Apple	O
released	O
the	O
Apple	O
PC	O
5.25	B-Device
"	I-Device
Drive	O
which	O
required	O
a	O
separate	O
custom	O
PC	O
5.25	O
Floppy	B-Device
Disk	I-Device
Controller	B-General_Concept
Card	I-General_Concept
,	O
different	O
for	O
each	O
Mac	O
model	O
.	O
</s>
<s>
It	O
is	O
the	O
only	O
-inch	O
drive	O
manufactured	O
by	O
Apple	O
that	O
can	O
be	O
used	O
by	O
the	O
Macintosh	B-Device
.	O
</s>
<s>
This	O
drive	O
was	O
for	O
use	O
with	O
industry	O
standard	O
double-sided	O
-inch	O
360-kilobyte	O
formatted	O
flexible	B-Device
disks	I-Device
.	O
</s>
<s>
Through	O
the	O
use	O
of	O
a	O
special	O
Macintosh	B-Device
Apple	B-Application
File	I-Application
Exchange	I-Application
utility	O
shipped	O
with	O
it	O
,	O
the	O
drive	O
could	O
read	O
files	O
from	O
,	O
and	O
write	O
files	O
to	O
,	O
floppy	B-Device
disks	I-Device
in	O
MS-DOS	B-Application
formats	O
.	O
</s>
<s>
Software	O
"	O
translators	O
"	O
could	O
convert	O
documents	O
between	O
WordStar	B-Application
and	O
MacWrite	B-Operating_System
formats	O
,	O
among	O
others	O
.	O
</s>
<s>
The	O
drive	O
is	O
incompatible	O
with	O
all	O
Apple	B-Device
II	I-Device
computers	O
and	O
the	O
Apple	B-Device
IIe	I-Device
Card	I-Device
for	O
the	O
Macintosh	B-Device
LC	I-Device
as	O
well	O
;	O
it	O
also	O
does	O
not	O
allow	O
a	O
Macintosh	B-Device
to	O
read	O
from	O
or	O
write	O
to	O
-inch	O
Apple	O
II-formatted	O
disks	O
.	O
</s>
<s>
This	O
drive	O
was	O
made	O
obsolete	O
by	O
the	O
industry-wide	O
adoption	O
of	O
-inch	O
disks	O
and	O
was	O
replaced	O
by	O
the	O
-inch	O
Apple	O
FDHD	B-Device
Drive	O
,	O
which	O
could	O
read	O
and	O
write	O
every	O
existing	O
Macintosh	B-Device
,	O
DOS	B-Application
and	O
Windows	B-Application
format	O
,	O
and	O
the	O
Apple	B-Device
II	I-Device
ProDOS	O
format	O
as	O
well	O
.	O
</s>
<s>
This	O
table	O
shows	O
the	O
pinout	O
of	O
the	O
original	O
1979	O
Disk	B-Device
II	I-Device
controller	O
and	O
newer	O
1983	O
Uni/Duo	O
Disk	O
I/O	O
controller	O
(	O
655-0101	O
)	O
.	O
</s>
<s>
The	O
Disk	B-Device
II	I-Device
header	O
pin	O
numbering	O
is	O
per	O
the	O
Disk	B-Device
II	I-Device
controller	B-General_Concept
card	I-General_Concept
silkscreen	O
and	O
the	O
circuit	O
schematic	O
given	O
in	O
the	O
DOS	B-Application
3.3	O
manual	O
.	O
</s>
<s>
The	O
EXTINT*	O
signal	O
is	O
not	O
present	O
on	O
the	O
Disk	B-Device
II	I-Device
controller	B-General_Concept
card	I-General_Concept
.	O
</s>
