<s>
The	O
XF551	O
was	O
the	O
last	O
floppy	B-Device
disk	I-Device
drive	I-Device
produced	O
by	O
Atari	O
for	O
the	O
8-bit	B-Device
series	I-Device
home	O
computers	O
.	O
</s>
<s>
Although	O
an	O
XE-styled	O
drive	O
was	O
shown	O
several	O
times	O
during	O
1985	O
and	O
1986	O
,	O
production	O
waited	O
while	O
leftover	O
inventories	O
of	O
the	O
Atari	B-Device
1050	I-Device
were	O
sold	O
off	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
the	O
success	O
of	O
the	O
Nintendo	O
Entertainment	O
System	O
(	O
NES	O
)	O
prompted	O
Atari	O
to	O
repackage	O
their	O
65XE	B-Device
as	O
the	O
Atari	B-General_Concept
XEGS	I-General_Concept
games	O
console	O
,	O
boasting	O
it	O
could	O
be	O
expanded	O
to	O
a	O
complete	O
computer	O
with	O
the	O
addition	O
of	O
a	O
keyboard	O
and	O
disk	O
drive	O
.	O
</s>
<s>
Its	O
release	O
was	O
marred	O
by	O
packaging	O
it	O
with	O
an	O
old	O
version	O
of	O
Atari	B-Operating_System
DOS	I-Operating_System
,	O
which	O
did	O
not	O
support	O
any	O
of	O
these	O
new	O
features	O
.	O
</s>
<s>
When	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
began	O
shipping	O
in	O
1979	O
,	O
Atari	O
showed	O
two	O
floppy	B-Device
disk	I-Device
drive	I-Device
systems	O
,	O
the	O
810	B-Device
and	O
the	O
815	O
.	O
</s>
<s>
The	O
810	B-Device
used	O
the	O
then-standard	O
single-density	O
FM	B-Protocol
encoding	I-Protocol
format	O
that	O
stored	O
about	O
90kB	O
of	O
data	O
,	O
while	O
the	O
815	O
packaged	O
two	O
drives	O
in	O
a	O
single	O
case	O
,	O
both	O
supporting	O
a	O
double-density	O
MFM	B-Protocol
encoding	I-Protocol
format	O
of	O
180kB	O
.	O
</s>
<s>
In	O
1983	O
,	O
Commodore	O
International	O
sparked	O
off	O
a	O
price	O
war	O
in	O
the	O
home	O
computer	O
market	O
by	O
repeatedly	O
lowering	O
the	O
price	O
of	O
its	O
VIC-20	B-Device
and	O
Commodore	O
64	O
(	O
C64	O
)	O
lines	O
in	O
order	O
to	O
undercut	O
the	O
TI-99/4A	B-Device
.	O
</s>
<s>
Atari	O
had	O
recently	O
introduced	O
the	O
Atari	O
1200XL	B-Device
at	O
a	O
higher	O
price	O
point	O
,	O
and	O
its	O
lineup	O
could	O
not	O
be	O
produced	O
profitably	O
at	O
the	O
rapidly	O
falling	O
market	O
prices	O
.	O
</s>
<s>
Atari	O
eventually	O
introduced	O
lower-cost	O
models	O
,	O
the	O
600XL	B-Device
and	O
800XL	B-Device
,	O
but	O
these	O
were	O
repeatedly	O
delayed	O
and	O
did	O
not	O
reach	O
market	O
until	O
late	O
in	O
1983	O
,	O
too	O
late	O
to	O
have	O
an	O
impact	O
.	O
</s>
<s>
Attempting	O
to	O
bring	O
the	O
company	O
back	O
to	O
some	O
semblance	O
of	O
profitability	O
,	O
the	O
new	O
management	O
laid	O
off	O
whole	O
divisions	O
while	O
working	O
to	O
bring	O
their	O
new	O
Atari	B-Device
ST	I-Device
,	O
to	O
market	O
as	O
soon	O
as	O
possible	O
.	O
</s>
<s>
This	O
replaced	O
the	O
original	O
custom	O
MOS	O
6507-based	O
interface	O
card	O
with	O
one	O
using	O
the	O
Intel	B-Device
8048	I-Device
microcontroller	B-Architecture
.	O
</s>
<s>
The	O
8048	B-Device
included	O
internal	O
RAM	O
and	O
ROM	O
and	O
thus	O
greatly	O
simplified	O
the	O
overall	O
design	O
of	O
the	O
interface	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
Atari	O
had	O
warehouses	O
of	O
the	O
Atari	B-General_Concept
5200	I-General_Concept
and	O
Atari	B-General_Concept
7800	I-General_Concept
which	O
were	O
put	O
back	O
on	O
the	O
market	O
,	O
but	O
neither	O
had	O
been	O
in	O
production	O
for	O
some	O
time	O
and	O
were	O
built	O
on	O
pre-XE	O
systems	O
with	O
no	O
capability	O
to	O
produce	O
more	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
decision	O
to	O
introduce	O
a	O
new	O
console	O
,	O
the	O
Atari	B-General_Concept
XEGS	I-General_Concept
,	O
which	O
was	O
essentially	O
a	O
repackaged	O
Atari	B-Device
65XE	I-Device
and	O
would	O
run	O
existing	O
8-bit	O
games	O
.	O
</s>
<s>
As	O
part	O
of	O
the	O
XEGS	B-General_Concept
launch	O
,	O
Atari	O
boasted	O
about	O
its	O
large	O
library	O
of	O
software	O
as	O
well	O
as	O
its	O
ability	O
to	O
be	O
used	O
as	O
a	O
true	O
computer	O
with	O
the	O
supplied	O
keyboard	O
and	O
optional	O
peripherals	O
including	O
a	O
floppy	B-Device
drive	I-Device
.	O
</s>
<s>
Nintendo	O
sued	O
Atari	O
for	O
false	O
advertising	O
,	O
noting	O
that	O
Atari	O
claimed	O
the	O
system	O
supported	O
a	O
floppy	B-Device
but	O
did	O
not	O
actually	O
have	O
drives	O
for	O
sale	O
.	O
</s>
<s>
Moreover	O
,	O
after	O
the	O
introduction	O
of	O
the	O
IBM	B-Device
PC	I-Device
,	O
drives	O
using	O
the	O
standard	O
34-bit	O
ribbon	O
cable	O
had	O
proliferated	O
.	O
</s>
<s>
Earlier	O
Atari	O
drives	O
used	O
a	O
customized	O
controller	O
that	O
communicated	O
with	O
the	O
host	O
computer	O
's	O
Atari	B-Architecture
SIO	I-Architecture
bus	O
using	O
a	O
6507	B-General_Concept
running	O
at	O
500kHz	O
.	O
</s>
<s>
Third	O
party	O
drives	O
normally	O
used	O
higher	O
speeds	O
,	O
when	O
run	O
with	O
suitable	O
third-party	O
DOSes	O
,	O
with	O
some	O
operating	O
as	O
high	O
as	O
the	O
52kbps	O
"	O
Warp	O
Speed	O
"	O
of	O
the	O
Happy	B-Device
810	I-Device
.	O
</s>
<s>
Atari	B-Operating_System
DOS	I-Operating_System
2.5	O
,	O
introduced	O
for	O
the	O
1050	O
in	O
1983	O
,	O
did	O
not	O
support	O
either	O
capability	O
.	O
</s>
<s>
Among	O
these	O
was	O
DOS	B-Application
XL	I-Application
,	O
introduced	O
in	O
1983	O
by	O
Optimized	B-Operating_System
Systems	I-Operating_System
Software	I-Operating_System
(	O
OSS	O
)	O
,	O
authors	O
of	O
the	O
original	O
Atari	B-Operating_System
DOS	I-Operating_System
.	O
</s>
<s>
When	O
the	O
lawsuit	O
was	O
launched	O
,	O
Atari	O
put	O
the	O
drive	O
on	O
the	O
market	O
immediately	O
in	O
June	O
1987	O
,	O
shipping	O
it	O
with	O
the	O
existing	O
Atari	B-Operating_System
DOS	I-Operating_System
2.5	O
.	O
</s>
<s>
The	O
only	O
real	O
complaints	O
were	O
the	O
rear	O
position	O
of	O
the	O
power	O
button	O
,	O
which	O
made	O
it	O
difficult	O
to	O
access	O
in	O
some	O
computer	O
desks	O
,	O
and	O
that	O
it	O
was	O
very	O
"	O
fussy	O
"	O
about	O
the	O
diskettes	B-Device
,	O
rejecting	O
as	O
many	O
as	O
20%	O
of	O
low-cost	O
floppies	B-Device
.	O
</s>
<s>
In	O
the	O
end	O
,	O
it	O
was	O
"	O
heartily	O
recommend	O
"	O
ed	O
,	O
and	O
"	O
the	O
best	O
thing	O
that	O
's	O
happened	O
to	O
Atari	O
's	O
8-bit	O
computer	O
line	O
since	O
the	O
birth	O
of	O
the	O
130XE	B-Device
"	O
.	O
</s>
<s>
These	O
markets	O
were	O
so	O
cost-sensitive	O
that	O
even	O
the	O
low	O
price	O
of	O
the	O
XF551	O
was	O
too	O
much	O
for	O
most	O
users	O
,	O
and	O
the	O
most	O
common	O
storage	O
mechanism	O
was	O
the	O
XC12	B-Device
cassette	B-Device
tape	I-Device
system	O
.	O
</s>
<s>
The	O
entire	O
8-bit	B-Device
series	I-Device
was	O
eventually	O
discontinued	O
in	O
1992	O
.	O
</s>
<s>
It	O
connected	O
to	O
the	O
computer	O
or	O
XEGS	B-General_Concept
using	O
the	O
SIO	O
port	O
,	O
with	O
two	O
ports	O
on	O
the	O
back	O
,	O
in	O
and	O
out	O
,	O
to	O
allow	O
it	O
to	O
be	O
daisy	O
chained	O
to	O
other	O
peripherals	O
.	O
</s>
<s>
When	O
operating	O
in	O
legacy	O
modes	O
to	O
read	O
or	O
write	O
to	O
disks	O
from	O
the	O
810	B-Device
or	O
1050	O
,	O
the	O
system	O
transferred	O
data	O
at	O
the	O
original	O
standard	O
speed	O
of	O
19,040	O
bps	O
.	O
</s>
<s>
In	O
previous	O
Atari	O
drives	O
,	O
this	O
had	O
been	O
accomplished	O
with	O
the	O
6507	B-General_Concept
,	O
a	O
cut-down	O
version	O
of	O
the	O
MOS	B-General_Concept
6502	I-General_Concept
that	O
was	O
being	O
used	O
in	O
the	O
Atari	B-Application
VCS	I-Application
console	O
.	O
</s>
<s>
The	O
console	O
ran	O
at	O
1.1MHz	O
,	O
but	O
some	O
6507s	B-General_Concept
supplied	O
by	O
Synertek	O
failed	O
to	O
run	O
at	O
this	O
speed	O
reliably	O
and	O
were	O
passed	O
off	O
to	O
be	O
used	O
as	O
SIO	O
controllers	O
running	O
at	O
lower	O
speeds	O
.	O
</s>
<s>
For	O
the	O
new	O
drive	O
,	O
which	O
operated	O
at	O
higher	O
speeds	O
and	O
had	O
more	O
features	O
,	O
the	O
6507	B-General_Concept
was	O
replaced	O
by	O
the	O
Intel	B-Device
8040	I-Device
,	O
microcontrollers	B-Architecture
that	O
included	O
ROM	O
and	O
RAM	O
on	O
the	O
same	O
chip	O
and	O
thus	O
allowed	O
a	O
great	O
simplification	O
of	O
the	O
controller	O
.	O
</s>
<s>
The	O
8040	B-Device
versions	O
did	O
not	O
have	O
enough	O
ROM	O
for	O
the	O
entire	O
driver	O
,	O
so	O
later	O
models	O
moved	O
to	O
the	O
8050	B-Device
with	O
4kB	O
for	O
a	O
further	O
simplification	O
.	O
</s>
<s>
The	O
controller	O
was	O
paired	O
with	O
the	O
then-standard	O
Western	B-Device
Digital	I-Device
FD1772	I-Device
floppy	B-Device
disk	I-Device
controller	O
,	O
a	O
late-model	O
version	O
of	O
WD	O
's	O
drive	O
controllers	O
that	O
implemented	O
almost	O
all	O
of	O
the	O
required	O
circuitry	O
in	O
a	O
single	O
28-pin	O
chip	O
and	O
thereby	O
lowered	O
the	O
total	O
cost	O
of	O
implementation	O
.	O
</s>
<s>
Previous	O
to	O
the	O
XF551	O
,	O
users	O
would	O
generally	O
use	O
both	O
sides	O
of	O
a	O
floppy	B-Device
disk	I-Device
by	O
formatting	O
one	O
side	O
,	O
flipping	O
the	O
disk	O
over	O
,	O
and	O
formatting	O
the	O
second	O
,	O
the	O
so-called	O
"	O
flippy	O
disk	O
"	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
810	B-Device
and	O
1050	O
,	O
which	O
ran	O
at	O
the	O
non-standard	O
speed	O
of	O
288RPM	O
,	O
the	O
XF551	O
ran	O
at	O
the	O
industry	O
standard	O
300RPM	O
.	O
</s>
<s>
This	O
caused	O
problems	O
for	O
a	O
small	O
number	O
of	O
programs	O
whose	O
copy	B-Application
protection	I-Application
relied	O
on	O
accurately	O
timing	O
the	O
drive	O
.	O
</s>
<s>
One	O
design	O
feature	O
of	O
DOS	O
XE	O
was	O
that	O
it	O
always	O
wrote	O
files	O
to	O
side	O
one	O
of	O
the	O
floppy	B-Device
until	O
it	O
ran	O
out	O
of	O
room	O
.	O
</s>
