<s>
FileWare	B-Device
floppy	B-Device
disk	I-Device
drives	I-Device
and	O
diskettes	B-Device
were	O
designed	O
by	O
Apple	O
Computer	O
as	O
a	O
higher-performance	O
alternative	O
to	O
the	O
Disk	B-Device
II	I-Device
and	O
Disk	O
III	O
floppy	B-Device
systems	O
used	O
on	O
the	O
Apple	B-Device
II	I-Device
and	O
Apple	B-Device
III	I-Device
personal	O
computers	O
.	O
</s>
<s>
The	O
drives	O
are	O
named	O
Apple	B-Device
871	I-Device
in	O
service	O
documentation	O
,	O
based	O
on	O
their	O
approximate	O
formatted	O
storage	O
capacity	O
in	O
kilobytes	O
,	O
but	O
are	O
most	O
commonly	O
known	O
by	O
their	O
codename	O
,	O
Twiggy	O
,	O
after	O
the	O
famously	O
thin	O
1960s	O
fashion	O
model	O
named	O
Twiggy	O
.	O
</s>
<s>
In	O
1978	O
,	O
Apple	O
intended	O
to	O
develop	O
its	O
own	O
FileWare	B-Device
drive	O
mechanism	O
for	O
use	O
in	O
the	O
new	O
Apple	B-Device
III	I-Device
and	O
Apple	B-Device
Lisa	I-Device
business	O
computers	O
being	O
developed	O
.	O
</s>
<s>
They	O
quickly	O
ran	O
into	O
difficulties	O
which	O
precluded	O
them	O
from	O
being	O
incorporated	O
in	O
the	O
Apple	B-Device
III	I-Device
,	O
which	O
continued	O
to	O
use	O
the	O
earlier	O
Shugart	O
design	O
.	O
</s>
<s>
Finally	O
,	O
FileWare	B-Device
drives	O
were	O
implemented	O
in	O
the	O
Lisa	B-Device
computer	O
,	O
released	O
on	O
January	O
19	O
,	O
1983	O
.	O
</s>
<s>
The	O
original	O
Macintosh	B-Device
computer	O
was	O
originally	O
intended	O
to	O
implement	O
a	O
Shugart	O
drive	O
,	O
then	O
later	O
,	O
a	O
FileWare	B-Device
drive	O
,	O
before	O
eventually	O
shipping	O
with	O
Sony	O
's	O
3.5	B-Device
"	I-Device
400k	O
diskette	B-Device
drive	O
.	O
</s>
<s>
Although	O
Apple	O
planned	O
to	O
make	O
FileWare	B-Device
drives	O
available	O
for	O
the	O
Apple	B-Device
II	I-Device
and	O
Apple	B-Device
III	I-Device
,	O
and	O
announced	O
them	O
under	O
the	O
names	O
UniFile	B-Device
and	O
DuoFile	B-Device
(	O
for	O
single	O
and	O
dual	O
drives	O
,	O
respectively	O
)	O
,	O
these	O
products	O
were	O
never	O
shipped	O
.	O
</s>
<s>
FileWare	B-Device
drives	O
are	O
5¼-inch	O
double-sided	O
,	O
but	O
are	O
not	O
mechanically	O
compatible	O
with	O
industry-standard	O
diskettes	B-Device
.	O
</s>
<s>
In	O
a	O
single-sided	O
floppy	B-Device
disk	I-Device
drive	I-Device
,	O
the	O
disk	B-Device
head	I-Device
is	O
opposed	O
by	O
a	O
foam	O
pressure	O
pad	O
.	O
</s>
<s>
In	O
a	O
normal	O
double-sided	O
floppy	B-Device
disk	I-Device
drive	I-Device
,	O
the	O
top	O
and	O
bottom	O
heads	O
are	O
almost	O
directly	O
opposed	O
to	O
each	O
other	O
.	O
</s>
<s>
Apple	O
was	O
concerned	O
about	O
head	O
wear	O
,	O
and	O
instead	O
designed	O
the	O
FileWare	B-Device
drive	O
such	O
that	O
the	O
top	O
and	O
bottom	O
heads	O
are	O
on	O
opposite	O
sides	O
of	O
the	O
spindle	O
,	O
and	O
each	O
is	O
opposed	O
by	O
a	O
pressure	O
pad	O
.	O
</s>
<s>
Since	O
there	O
is	O
only	O
one	O
actuator	B-Algorithm
to	O
move	O
the	O
heads	O
,	O
when	O
one	O
head	O
is	O
near	O
the	O
spindle	O
,	O
the	O
other	O
is	O
near	O
the	O
outer	O
rim	O
of	O
the	O
disk	O
.	O
</s>
<s>
The	O
drive	O
is	O
approximately	O
the	O
same	O
size	O
as	O
a	O
standard	O
full-height	O
5¼	O
inch	O
floppy	B-Device
drive	I-Device
,	O
but	O
does	O
not	O
use	O
the	O
standard	O
mounting	O
hole	O
locations	O
.	O
</s>
<s>
The	O
electrical	O
interface	O
is	O
completely	O
different	O
from	O
that	O
of	O
standard	O
drives	O
,	O
though	O
conceptually	O
similar	O
to	O
that	O
of	O
the	O
Disk	B-Device
II	I-Device
.	O
</s>
<s>
The	O
FileWare	B-Device
diskette	B-Device
has	O
the	O
same	O
overall	O
jacket	O
dimensions	O
of	O
a	O
normal	O
5¼	O
inch	O
diskette	B-Device
,	O
but	O
because	O
of	O
the	O
head	O
arrangement	O
,	O
the	O
jacket	O
has	O
non-standard	O
cutouts	O
for	O
the	O
heads	O
,	O
with	O
two	O
sets	O
of	O
cutouts	O
on	O
opposite	O
sides	O
of	O
the	O
spindle	O
hole	O
.	O
</s>
<s>
The	O
write	O
enable	O
sensor	O
is	O
also	O
in	O
a	O
non-standard	O
location	O
,	O
though	O
most	O
FileWare	B-Device
diskettes	B-Device
were	O
produced	O
without	O
a	O
write	O
protect	O
slot	O
.	O
</s>
<s>
The	O
jacket	O
had	O
a	O
corner	O
cutout	O
that	O
keyed	O
the	O
diskette	B-Device
to	O
prevent	O
insertion	O
in	O
an	O
incorrect	O
orientation	O
,	O
and	O
a	O
rectangular	O
hole	O
that	O
the	O
drive	O
could	O
use	O
to	O
latch	O
the	O
diskette	B-Device
in	O
place	O
,	O
preventing	O
removal	O
until	O
the	O
software	O
allowed	O
it	O
.	O
</s>
<s>
FileWare	B-Device
drives	O
use	O
62.5	O
tracks	B-Device
per	O
inch	O
rather	O
than	O
the	O
standard	O
48	O
or	O
96	O
TPI	O
,	O
and	O
use	O
high	O
flux	B-General_Concept
density	I-General_Concept
(	O
comparable	O
to	O
the	O
later	O
IBM	O
1.2MB	O
format	O
introduced	O
with	O
the	O
PC/AT	B-Operating_System
)	O
.	O
</s>
<s>
The	O
coercivity	O
required	O
is	O
similar	O
to	O
that	O
of	O
the	O
1.2MB	O
format	O
,	O
so	O
it	O
is	O
possible	O
to	O
modify	O
the	O
jacket	O
of	O
1.2MB	O
diskettes	B-Device
for	O
use	O
in	O
a	O
FileWare	B-Device
drive	O
.	O
</s>
<s>
The	O
disk	O
format	O
uses	O
group	B-Device
coded	I-Device
recording	I-Device
(	O
GCR	B-Device
)	O
in	O
a	O
manner	O
very	O
similar	O
to	O
that	O
of	O
the	O
Disk	B-Device
II	I-Device
.	O
</s>
<s>
The	O
drive	O
contains	O
circuitry	O
to	O
allow	O
software	O
control	O
over	O
the	O
motor	O
speed	O
,	O
which	O
is	O
used	O
to	O
maintain	O
near	O
constant	O
flux	B-General_Concept
transition	O
rate	O
on	O
all	O
tracks	B-Device
,	O
so	O
that	O
more	O
data	O
can	O
be	O
stored	O
on	O
the	O
outer	O
tracks	B-Device
.	O
</s>
<s>
Each	O
side	O
of	O
the	O
disk	O
had	O
46	O
tracks	B-Device
,	O
and	O
the	O
number	O
of	O
sectors	O
per	O
track	O
varies	O
from	O
15	O
to	O
22	O
.	O
</s>
<s>
The	O
Lisa	B-Device
Hardware	O
Manual	O
does	O
n't	O
explicitly	O
state	O
the	O
total	O
number	O
of	O
sectors	O
,	O
but	O
page	O
173	O
states	O
that	O
there	O
are	O
4	O
tracks	B-Device
of	O
22	O
sectors	O
,	O
7x21	O
,	O
6x20	O
,	O
6x19	O
,	O
6x18	O
,	O
6x17	O
,	O
7x16	O
,	O
and	O
4x15	O
.	O
</s>
<s>
The	O
controller	O
uses	O
similar	O
circuitry	O
to	O
the	O
Disk	B-Device
II	I-Device
controller	O
,	O
but	O
runs	O
at	O
twice	O
the	O
clock	O
rate	O
.	O
</s>
<s>
The	O
controller	O
uses	O
a	O
dedicated	O
MOS	B-Architecture
6504	O
microprocessor	O
;	O
in	O
the	O
Lisa	B-Device
this	O
is	O
on	O
the	O
system	O
I/O	B-Device
card	I-Device
,	O
and	O
for	O
the	O
UniFile/DuoFile	O
products	O
,	O
it	O
is	O
on	O
an	O
interface	O
card	O
that	O
plugs	O
into	O
a	O
peripheral	O
expansion	B-Device
slot	I-Device
.	O
</s>
<s>
The	O
Lisa	B-Device
2/10	O
and	O
Macintosh	B-Device
XL	I-Device
I/O	B-Device
card	I-Device
use	O
the	O
IWM	B-Device
controller	O
chip	O
to	O
replace	O
the	O
TTL	B-General_Concept
chips	O
of	O
the	O
earlier	O
design	O
.	O
</s>
<s>
FileWare	B-Device
drives	O
proved	O
to	O
be	O
somewhat	O
unreliable	O
.	O
</s>
<s>
In	O
early	O
1984	O
,	O
Apple	O
introduced	O
the	O
Lisa	B-Device
2	O
,	O
which	O
uses	O
a	O
single	O
3½inch	O
Sony	O
floppy	B-Device
drive	I-Device
in	O
place	O
of	O
the	O
two	O
FileWare	B-Device
drives	O
of	O
the	O
original	O
Lisa	B-Device
.	O
</s>
<s>
A	O
free	O
upgrade	O
was	O
offered	O
to	O
Lisa	B-Device
1	O
owners	O
.	O
</s>
