<s>
The	O
Atari	B-Protocol
joystick	I-Protocol
port	I-Protocol
is	O
a	O
computer	B-Protocol
port	I-Protocol
used	O
to	O
connect	O
various	O
gaming	O
controllers	O
to	O
game	B-Device
console	I-Device
and	O
home	O
computer	O
systems	O
in	O
the	O
1970s	O
to	O
the	O
1990s	O
.	O
</s>
<s>
It	O
was	O
originally	O
introduced	O
on	O
the	O
Atari	B-General_Concept
2600	I-General_Concept
in	O
1977	O
and	O
then	O
used	O
on	O
the	O
Atari	B-Device
400	I-Device
and	I-Device
800	I-Device
in	O
1979	O
.	O
</s>
<s>
It	O
went	O
cross-platform	O
with	O
the	O
VIC-20	B-Device
in	O
1981	O
,	O
and	O
was	O
then	O
used	O
on	O
many	O
following	O
machines	O
from	O
both	O
companies	O
,	O
as	O
well	O
as	O
a	O
growing	O
list	O
of	O
3rd	O
party	O
machines	O
like	O
the	O
MSX	B-Operating_System
platform	O
and	O
various	O
Sega	O
consoles	O
.	O
</s>
<s>
The	O
port	O
,	O
based	O
on	O
the	O
inexpensive	O
9-pin	O
D-connector	B-Protocol
,	O
became	O
a	O
de	O
facto	O
standard	O
through	O
the	O
1980s	O
and	O
into	O
the	O
1990s	O
,	O
supported	O
by	O
a	O
wide	O
variety	O
of	O
joysticks	O
and	O
other	O
devices	O
,	O
most	O
commonly	O
paddle	B-Device
controllers	I-Device
,	O
light	B-Device
pens	I-Device
and	O
computer	B-Device
mice	I-Device
.	O
</s>
<s>
The	O
standard	O
was	O
so	O
engrained	O
that	O
it	O
led	O
to	O
devices	O
like	O
the	O
Kempston	O
Interface	O
that	O
allowed	O
Atari	O
joysticks	O
to	O
be	O
used	O
on	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
.	O
</s>
<s>
The	O
port	O
was	O
also	O
used	O
for	O
all	O
sorts	O
of	O
non-gaming	O
roles	O
,	O
including	O
the	O
AtariLab	B-Application
interface	O
,	O
modems	B-Application
,	O
numeric	B-Device
keypads	I-Device
,	O
and	O
even	O
a	O
video	O
expansion	O
card	O
.	O
</s>
<s>
By	O
the	O
mid-1990s	O
,	O
the	O
last	O
home	O
computer	O
and	O
game	B-Device
console	I-Device
models	O
using	O
Atari	O
ports	O
–	O
often	O
for	O
both	O
joystick	O
and	O
mouse	O
–	O
were	O
discontinued	O
.	O
</s>
<s>
IBM	O
PC-compatible	O
computers	O
,	O
which	O
did	O
not	O
have	O
Atari	B-Protocol
joystick	I-Protocol
ports	I-Protocol
,	O
became	O
dominant	O
in	O
the	O
home	O
computer	O
market	O
,	O
and	O
console	O
manufacturers	O
such	O
as	O
Sega	O
switched	O
to	O
other	O
types	O
of	O
ports	O
.	O
</s>
<s>
The	O
Atari	B-General_Concept
Video	I-General_Concept
Computer	I-General_Concept
System	I-General_Concept
(	O
later	O
the	O
2600	O
)	O
developed	O
out	O
of	O
an	O
effort	O
to	O
address	O
problems	O
Atari	O
found	O
when	O
releasing	O
their	O
first	O
home	O
video	B-Device
game	I-Device
console	I-Device
,	O
Pong	B-Application
.	O
</s>
<s>
Although	O
successful	O
,	O
Pong	B-Application
was	O
an	O
expensive	O
system	O
to	O
design	O
,	O
and	O
was	O
dedicated	O
solely	O
to	O
one	O
game	O
.	O
</s>
<s>
The	O
list	O
of	O
games	O
it	O
would	O
need	O
to	O
support	O
included	O
Pong	B-Application
variations	O
,	O
and	O
Tank	B-Application
.	O
</s>
<s>
It	O
was	O
the	O
desire	O
to	O
run	O
these	O
two	O
games	O
that	O
led	O
to	O
the	O
need	O
for	O
some	O
sort	O
of	O
flexible	O
input	O
system	O
;	O
Pong	B-Application
used	O
analog	O
paddle	B-Device
controllers	I-Device
,	O
while	O
Tank	B-Application
used	O
dual	O
digital	O
(	O
on/off	O
)	O
joysticks	O
.	O
</s>
<s>
Arcade	O
games	O
of	O
the	O
era	O
generally	O
used	O
paddles	B-Device
,	O
joysticks	O
or	O
a	O
unique	O
sort	O
of	O
steering	O
wheel	O
controller	O
that	O
was	O
spun	O
,	O
entirely	O
unlike	O
a	O
real	O
car	O
.	O
</s>
<s>
Development	O
of	O
the	O
2600	O
was	O
strictly	O
a	O
paper	O
project	O
until	O
September	O
1975	O
,	O
when	O
the	O
MOS	B-General_Concept
Technology	I-General_Concept
6502	I-General_Concept
processor	O
was	O
released	O
.	O
</s>
<s>
The	O
6502	B-General_Concept
offered	O
the	O
right	O
combinations	O
of	O
features	O
,	O
performance	O
and	O
price	O
that	O
made	O
a	O
console	O
using	O
ROM	B-Protocol
cartridges	I-Protocol
for	O
program	O
storage	O
practical	O
for	O
the	O
first	O
time	O
.	O
</s>
<s>
As	O
part	O
of	O
this	O
effort	O
,	O
Joe	O
Decuir	O
began	O
development	O
of	O
an	O
I/O	O
system	O
based	O
primarily	O
on	O
the	O
MOS	B-Device
Technology	I-Device
6532	I-Device
,	O
which	O
included	O
8-bit	O
I/O	O
ports	O
as	O
well	O
as	O
the	O
hardware	O
needed	O
to	O
control	O
memory	O
refresh	O
and	O
similar	O
housekeeping	O
tasks	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
TIA	B-General_Concept
,	O
whose	O
primary	O
task	O
was	O
sound	O
and	O
video	O
,	O
was	O
used	O
to	O
handle	O
timing-based	O
controllers	O
like	O
paddles	B-Device
and	O
light	B-Device
pens	I-Device
.	O
</s>
<s>
The	O
physical	O
interface	O
was	O
the	O
9-pin	B-Protocol
D-sub	I-Protocol
connector	I-Protocol
,	O
which	O
was	O
already	O
relatively	O
common	O
for	O
reduced	O
pin-count	O
serial	B-Protocol
ports	I-Protocol
on	O
the	O
Apple	B-Device
II	I-Device
and	O
S-100	B-Architecture
bus	I-Architecture
machines	O
.	O
</s>
<s>
The	O
2600	O
was	O
released	O
in	O
1977	O
,	O
shipping	O
with	O
both	O
the	O
paddle	B-Device
controllers	I-Device
and	O
a	O
single	O
joystick	O
.	O
</s>
<s>
Most	O
game	O
consoles	O
before	O
the	O
Atari	O
had	O
paddle	B-Device
controllers	I-Device
,	O
even	O
detachable	O
ones	O
in	O
the	O
case	O
of	O
the	O
Fairchild	B-Operating_System
Channel	I-Operating_System
F	I-Operating_System
and	O
Magnavox	B-Device
Odyssey	I-Device
.	O
</s>
<s>
But	O
the	O
joystick	O
was	O
new	O
,	O
and	O
quickly	O
garnered	O
praise	O
as	O
it	O
allowed	O
direct	O
input	O
into	O
a	O
number	O
of	O
games	O
that	O
would	O
otherwise	O
be	O
difficult	O
to	O
control	O
using	O
a	O
paddle	B-Device
.	O
</s>
<s>
As	O
1979	O
approached	O
the	O
home	O
computer	O
market	O
emerged	O
,	O
and	O
Atari	O
repositioned	O
the	O
new	O
system	O
as	O
the	O
400	O
and	O
800	O
,	O
the	O
first	O
members	O
of	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
.	O
</s>
<s>
Included	O
among	O
the	O
non-controller	O
devices	O
was	O
the	O
AtariLab	B-Application
system	O
that	O
allowed	O
users	O
to	O
plug	O
in	O
various	O
laboratory	O
devices	O
like	O
digital	O
thermometers	O
,	O
the	O
300baud	O
MPP-1000C	O
modem	B-Application
,	O
and	O
even	O
Atari	O
's	O
own	O
80-column	O
adaptor	O
for	O
the	O
8-bit	O
series	O
,	O
the	O
XEP80	O
.	O
</s>
<s>
Commodore	O
included	O
an	O
Atari	B-Protocol
joystick	I-Protocol
port	I-Protocol
with	O
the	O
VIC-20	B-Device
computer	O
.	O
</s>
<s>
Atari	O
had	O
patents	O
on	O
the	O
joystick	O
and	O
won	O
an	O
injunction	O
against	O
Commodore	O
,	O
which	O
produced	O
an	O
almost	O
identical	O
"	O
imitation	O
"	O
joystick	O
for	O
the	O
VIC-20	B-Device
,	O
but	O
held	O
no	O
patents	O
on	O
the	O
port	O
itself	O
.	O
</s>
<s>
By	O
the	O
time	O
Commodore	O
began	O
development	O
of	O
the	O
VIC-20	B-Device
millions	O
of	O
controllers	O
compatible	O
with	O
the	O
port	O
were	O
in	O
the	O
market	O
.	O
</s>
<s>
The	O
Atari	B-Protocol
joystick	I-Protocol
port	I-Protocol
rapidly	O
proliferated	O
across	O
the	O
industry	O
.	O
</s>
<s>
Hundreds	O
of	O
new	O
devices	O
using	O
the	O
system	O
cropped	O
up	O
over	O
time	O
,	O
including	O
trackballs	B-Device
and	O
other	O
advanced	O
inputs	O
.	O
</s>
<s>
The	O
standard	O
became	O
so	O
widely	O
used	O
that	O
almost	O
every	O
8-bit	O
machine	O
released	O
after	O
1982	O
used	O
it	O
,	O
and	O
adapters	O
were	O
available	O
for	O
those	O
that	O
did	O
not	O
,	O
like	O
the	O
Apple	B-Device
II	I-Device
and	O
ZX	B-Operating_System
Spectrum	I-Operating_System
.	O
</s>
<s>
One	O
TI-99/4A	B-Device
reseller	O
reported	O
that	O
its	O
best-selling	O
product	O
was	O
the	O
Atari	O
joystick	O
adapter	O
.	O
</s>
<s>
The	O
port	O
moved	O
to	O
16/32	O
-bit	O
machines	O
like	O
the	O
Atari	B-Device
ST	I-Device
and	O
Amiga	B-Device
as	O
well	O
.	O
</s>
<s>
The	O
introduction	O
of	O
the	O
Nintendo	O
Entertainment	O
System	O
was	O
the	O
first	O
widespread	O
example	O
of	O
a	O
gaming	O
system	O
in	O
that	O
era	O
that	O
did	O
not	O
use	O
the	O
Atari	O
design	O
,	O
its	O
D-pad	B-Device
having	O
been	O
designed	O
specifically	O
to	O
be	O
less	O
bulky	O
.	O
</s>
<s>
Meanwhile	O
,	O
the	O
IBM	B-Device
PC	I-Device
had	O
introduced	O
the	O
15-pin	O
game	B-Protocol
port	I-Protocol
that	O
was	O
designed	O
primarily	O
for	O
analog	O
inputs	O
,	O
but	O
use	O
remained	O
rare	O
until	O
the	O
introduction	O
of	O
popular	O
flight	B-Application
simulators	I-Application
.	O
</s>
<s>
By	O
the	O
mid-1990s	O
,	O
the	O
Atari	O
standard	O
was	O
becoming	O
obsolete	O
when	O
home	O
computers	O
like	O
Atari	B-Device
ST	I-Device
and	O
Amiga	B-Device
exited	O
markets	O
along	O
with	O
Sega	B-Operating_System
Genesis	I-Operating_System
game	B-Device
console	I-Device
.	O
</s>
<s>
With	O
the	O
Atari	O
STE	O
Atari	O
introduced	O
the	O
enhanced	O
joystick	B-Protocol
port	I-Protocol
(	O
15	O
pin	O
dsub	B-Protocol
)	O
alongside	O
the	O
2	O
joystick	B-Protocol
ports	I-Protocol
from	O
Atari	B-Device
ST	I-Device
,	O
and	O
when	O
the	O
Jaguar	B-Device
was	O
released	O
,	O
they	O
only	O
used	O
the	O
enhanced	O
joystick	B-Protocol
port	I-Protocol
.	O
</s>
<s>
There	O
have	O
also	O
been	O
numerous	O
systems	O
to	O
allow	O
the	O
ports	O
to	O
be	O
adapted	O
to	O
Universal	B-Protocol
Serial	I-Protocol
Bus	I-Protocol
,	O
and	O
even	O
entirely	O
new	O
Atari-like	O
joystick	O
designs	O
using	O
USB	B-Protocol
.	O
</s>
<s>
The	O
Atari	B-Protocol
joystick	I-Protocol
port	I-Protocol
used	O
a	O
9-pin	O
male	O
socket	O
in	O
the	O
host	O
system	O
,	O
and	O
female	O
connectors	O
on	O
the	O
devices	O
.	O
</s>
<s>
The	O
instantaneous	O
values	O
were	O
polled	O
30	O
times	O
a	O
second	O
during	O
the	O
vertical	O
blank	O
interrupt	O
(	O
VBI	O
)	O
when	O
the	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
handled	O
a	O
number	O
of	O
housekeeping	O
tasks	O
.	O
</s>
<s>
Depending	O
on	O
settings	O
in	O
other	O
registers	O
,	O
the	O
inputs	O
on	O
the	O
pins	O
were	O
interpreted	O
in	O
a	O
number	O
of	O
ways	O
and	O
then	O
the	O
output	O
data	O
was	O
placed	O
in	O
a	O
number	O
of	O
RAM	B-Architecture
registers	O
.	O
</s>
<s>
Atari	O
referred	O
to	O
this	O
copying	O
from	O
hardware	O
to	O
the	O
RAM	B-Architecture
as	O
"	O
shadowing	O
"	O
.	O
</s>
<s>
Driving	O
games	O
of	O
the	O
1980s	O
were	O
generally	O
top-down	O
and	O
used	O
a	O
unique	O
controller	O
that	O
would	O
cause	O
the	O
car	O
to	O
turn	O
at	O
a	O
fixed	O
rate	O
to	O
one	O
side	O
or	O
the	O
other	O
or	O
go	O
in	O
a	O
straight	O
line	O
(	O
Atari	O
's	O
Night	B-Application
Driver	I-Application
is	O
a	O
notable	O
exception	O
)	O
.	O
</s>
<s>
Paddles	B-Device
are	O
analog	O
devices	O
normally	O
used	O
to	O
control	O
horizontal	O
positioning	O
of	O
the	O
player	O
on	O
the	O
screen	O
.	O
</s>
<s>
On	O
the	O
Atari	O
systems	O
,	O
the	O
paddles	B-Device
were	O
connected	O
in	O
pairs	O
,	O
allowing	O
up	O
to	O
four	O
people	O
to	O
play	O
together	O
on	O
a	O
two-port	O
system	O
.	O
</s>
<s>
The	O
paddles	B-Device
worked	O
by	O
connecting	O
the	O
+5V	O
line	O
through	O
a	O
potentiometer	B-Device
(	O
pot	O
)	O
and	O
then	O
back	O
into	O
pins	O
5	O
and	O
9	O
,	O
one	O
for	O
each	O
paddle	B-Device
in	O
the	O
pair	O
.	O
</s>
<s>
One	O
advantage	O
to	O
this	O
system	O
was	O
the	O
color	O
clock	O
values	O
provided	O
by	O
the	O
paddle	B-Device
controllers	I-Device
were	O
the	O
same	O
numbers	O
that	O
controlled	O
the	O
horizontal	O
location	O
of	O
sprites	O
,	O
meaning	O
that	O
the	O
programmer	O
could	O
simply	O
copy	O
the	O
value	O
of	O
the	O
pot	O
shadow	O
register	O
into	O
the	O
sprite	O
's	O
horizontal	O
position	O
register	O
and	O
it	O
would	O
appear	O
at	O
the	O
appropriate	O
location	O
on-screen	O
.	O
</s>
<s>
Keyboard	O
controllers	O
were	O
used	O
in	O
the	O
Atari	O
systems	O
as	O
auxiliary	O
inputs	O
,	O
for	O
numeric	B-Device
keypads	I-Device
on	O
the	O
8-bit	O
machines	O
and	O
special	O
purpose	O
controllers	O
on	O
the	O
2600	O
,	O
like	O
the	O
Star	B-Application
Raiders	I-Application
port	O
.	O
</s>
<s>
Light	B-Device
pens	I-Device
were	O
directly	O
supported	O
as	O
well	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
a	O
phototransistor	O
in	O
the	O
light	B-Device
pen	I-Device
was	O
connected	O
to	O
the	O
trigger	O
line	O
of	O
the	O
port	O
.	O
</s>
<s>
If	O
placed	O
in	O
light	B-Device
pen	I-Device
mode	O
,	O
whenever	O
the	O
trigger	O
was	O
seen	O
to	O
go	O
low	O
,	O
the	O
OS	O
would	O
copy	O
the	O
color	O
clock	O
value	O
into	O
the	O
PENH	O
register	O
to	O
record	O
the	O
horizontal	O
position	O
,	O
and	O
the	O
VCOUNT	O
register	O
of	O
the	O
video	O
hardware	O
into	O
the	O
PENV	O
register	O
.	O
</s>
<s>
A	O
sprite	O
can	O
then	O
be	O
set	O
to	O
those	O
coordinates	O
and	O
will	O
appear	O
under	O
the	O
light	B-Device
pen	I-Device
.	O
</s>
<s>
Graphics	O
tablets	O
were	O
handled	O
using	O
the	O
same	O
hardware	O
as	O
the	O
paddle	B-Device
controllers	I-Device
,	O
encoding	O
the	O
X	O
axis	O
as	O
the	O
output	O
of	O
one	O
paddle	B-Device
and	O
the	O
Y	O
axis	O
as	O
the	O
other	O
.	O
</s>
<s>
The	O
stylus	O
button	O
was	O
connected	O
to	O
the	O
up	O
direction	O
of	O
the	O
joystick	B-Protocol
port	I-Protocol
,	O
while	O
the	O
left	O
and	O
right	O
buttons	O
on	O
the	O
tablet	O
itself	O
were	O
connected	O
to	O
two	O
of	O
the	O
trigger	O
inputs	O
.	O
</s>
<s>
Because	O
the	O
pins	O
of	O
the	O
joystick	O
were	O
wired	O
directly	O
to	O
the	O
input/output	O
controllers	O
on	O
the	O
motherboard	B-Device
,	O
it	O
was	O
possible	O
to	O
program	O
them	O
to	O
output	O
to	O
the	O
port	O
,	O
rather	O
than	O
input	O
.	O
</s>
<s>
A	O
device	B-Application
driver	I-Application
used	O
these	O
pins	O
to	O
implement	O
a	O
bidirectional	O
serial	B-Protocol
port	I-Protocol
,	O
which	O
worked	O
in	O
joystick	B-Protocol
port	I-Protocol
1	O
or	O
2	O
.	O
</s>
<s>
Similar	O
drivers	O
were	O
used	O
by	O
other	O
devices	O
,	O
like	O
modems	B-Application
,	O
which	O
avoided	O
the	O
need	O
to	O
use	O
the	O
more	O
expensive	O
Atari	B-Architecture
SIO	I-Architecture
system	O
.	O
</s>
<s>
The	O
VIC-20	B-Device
has	O
one	O
Control	O
Port	O
,	O
and	O
the	O
Commodore	O
64	O
had	O
two	O
ports	O
,	O
each	O
a	O
complete	O
implementation	O
of	O
the	O
Atari	O
standard	O
.	O
</s>
<s>
The	O
digital	O
pins	O
on	O
the	O
Commodore	O
64	O
's	O
control	O
ports	O
were	O
read	O
by	O
a	O
MOS	B-Device
Technology	I-Device
CIA	I-Device
chip	O
,	O
and	O
the	O
analog	O
paddle	B-Device
inputs	O
in	O
fashion	O
similar	O
to	O
the	O
Atari	O
by	O
the	O
MOS	O
Technology	O
SID	O
sound	O
chip	O
in	O
conjunction	O
with	O
a	O
timer	O
.	O
</s>
<s>
Light	B-Device
pens	I-Device
could	O
only	O
be	O
used	O
in	O
Control	O
Port	O
1	O
and	O
worked	O
in	O
a	O
similar	O
way	O
to	O
the	O
Atari	O
,	O
but	O
was	O
based	O
on	O
a	O
faster	O
clock	O
so	O
the	O
horizontal	O
axis	O
read	O
from	O
0	O
to	O
511	O
.	O
</s>
<s>
On	O
the	O
Atari	B-Device
ST	I-Device
,	O
the	O
two	O
ports	O
were	O
normally	O
configured	O
with	O
Port	O
0	O
set	O
to	O
mouse	O
mode	O
and	O
Port	O
1	O
to	O
joystick	O
.	O
</s>
<s>
The	O
ST	O
implementation	O
of	O
the	O
joystick	B-Protocol
port	I-Protocol
lacked	O
analog	O
input	O
,	O
the	O
following	O
STE	O
model	O
introduced	O
an	O
enhanced	O
joystick	B-Protocol
port	I-Protocol
which	O
used	O
a	O
15-pin	O
dsub	B-Protocol
that	O
had	O
analog	O
support	O
.	O
</s>
<s>
The	O
Commodore	B-Device
Amiga	I-Device
had	O
a	O
complete	O
two-port	O
implementation	O
known	O
as	O
gameports	B-Protocol
.	O
</s>
<s>
Unlike	O
earlier	O
systems	O
that	O
had	O
to	O
be	O
interpreted	O
by	O
examining	O
bits	O
in	O
registers	O
,	O
the	O
Amiga	B-Device
's	O
OS	O
had	O
a	O
number	O
of	O
drivers	O
and	O
libraries	O
that	O
made	O
interaction	O
simple	O
.	O
</s>
<s>
This	O
included	O
handlers	O
for	O
five	O
types	O
of	O
input	O
devices	O
,	O
include	O
mice	O
,	O
joysticks	O
,	O
light	B-Device
pens	I-Device
and	O
"	O
proportional	O
controllers	O
"	O
as	O
a	O
catch-all	O
for	O
analog	O
inputs	O
like	O
paddles	B-Device
and	O
analog	O
joysticks	O
.	O
</s>
<s>
The	O
TI-99/4A	B-Device
home	O
computer	O
series	O
used	O
a	O
9-pin	O
connector	O
that	O
was	O
physically	O
identical	O
to	O
the	O
Atari	O
version	O
,	O
as	O
well	O
as	O
being	O
similar	O
in	O
terms	O
of	O
the	O
devices	O
and	O
the	O
way	O
they	O
worked	O
.	O
</s>
<s>
The	O
ColecoVision	B-Device
game	B-Device
console	I-Device
extended	O
the	O
2600	O
controller	O
with	O
two	O
(	O
or	O
four	O
)	O
triggers	O
and	O
a	O
12	O
key	O
pad	O
.	O
</s>
<s>
The	O
ColecoVision	B-Device
also	O
supported	O
driving	O
controllers	O
and	O
trackballs	B-Device
.	O
</s>
<s>
Many	O
ColecoVision	B-Device
games	O
can	O
be	O
played	O
with	O
an	O
Atari-compatible	O
controller	O
,	O
if	O
a	O
Coleco	O
controller	O
is	O
plugged	O
into	O
the	O
second	O
port	O
and	O
used	O
to	O
select	O
the	O
game	O
.	O
</s>
<s>
The	O
Atari	B-General_Concept
7800	I-General_Concept
game	B-Device
console	I-Device
extended	O
the	O
2600	O
controller	O
with	O
a	O
second	O
trigger	O
.	O
</s>
<s>
MSX	B-Operating_System
home	O
computers	O
used	O
a	O
slightly	O
modified	O
version	O
of	O
the	O
port	O
,	O
replacing	O
one	O
of	O
the	O
analog	O
inputs	O
with	O
a	O
second	O
trigger	O
,	O
and	O
the	O
other	O
with	O
a	O
strobe	O
pin	O
.	O
</s>
<s>
The	O
strobe	O
pin	O
was	O
used	O
to	O
support	O
mouse	B-Device
input	I-Device
.	O
</s>
<s>
On	O
systems	O
like	O
the	O
ST	O
and	O
Amiga	B-Device
,	O
custom	O
hardware	O
was	O
used	O
to	O
carefully	O
track	O
these	O
in	O
order	O
for	O
the	O
motion	O
to	O
be	O
smoothly	O
followed	O
,	O
as	O
the	O
CPU	B-General_Concept
might	O
become	O
too	O
busy	O
with	O
other	O
tasks	O
to	O
follow	O
the	O
rapid	O
interrupts	O
.	O
</s>
<s>
Less	O
powerful	O
8-bit	O
designs	O
did	O
not	O
have	O
the	O
performance	O
to	O
smoothly	O
track	O
a	O
mouse	O
without	O
additional	O
hardware	O
,	O
and	O
the	O
MSX	B-Operating_System
designs	O
,	O
based	O
on	O
off-the-shelf	O
hardware	O
,	O
lacked	O
this	O
ability	O
.	O
</s>
<s>
MSX	B-Operating_System
mice	O
were	O
expensive	O
,	O
and	O
this	O
led	O
to	O
adaptors	O
for	O
PS/2	O
style	O
mice	O
,	O
which	O
operated	O
along	O
similar	O
principles	O
.	O
</s>
<s>
Sega	O
Master	O
System	O
and	O
Sega	B-Operating_System
Genesis	I-Operating_System
game	B-Device
console	I-Device
controllers	O
are	O
backwards-compatible	O
and	O
can	O
be	O
used	O
with	O
the	O
Atari	B-General_Concept
2600	I-General_Concept
.	O
</s>
<s>
Not	O
all	O
Magnavox	B-Application
Odyssey	I-Application
2	I-Application
systems	O
had	O
removable	O
controllers	O
.	O
</s>
<s>
Some	O
Amstrad	O
PCs	O
,	O
that	O
were	O
otherwise	O
IBM	B-Device
PC	I-Device
compatible	O
,	O
had	O
Atari-compatible	O
digital	O
gameports	B-Protocol
rather	O
than	O
the	O
PC	B-Protocol
analog	I-Protocol
standard	I-Protocol
.	O
</s>
<s>
Software	O
such	O
as	O
Elite	B-Application
and	O
GEM	B-Application
had	O
support	O
for	O
the	O
Amstrad	O
digital	O
gameport	B-Protocol
.	O
</s>
<s>
The	O
Apple	B-Device
II	I-Device
also	O
had	O
a	O
joystick	B-Protocol
port	I-Protocol
using	O
a	O
9-pin	O
D-sub	B-Protocol
,	O
but	O
it	O
was	O
a	O
very	O
different	O
system	O
that	O
connected	O
two	O
analog	O
joysticks	O
to	O
a	O
single	O
port	O
.	O
</s>
<s>
These	O
were	O
not	O
very	O
suitable	O
for	O
directional	O
games	O
,	O
and	O
adapters	O
for	O
Atari	O
port	O
devices	O
were	O
common	O
,	O
both	O
commercial	O
ones	O
like	O
the	O
Sirius	B-Device
Joyport	I-Device
,	O
as	O
well	O
as	O
many	O
home-brew	O
systems	O
.	O
</s>
<s>
These	O
adapters	O
did	O
not	O
allow	O
the	O
analog	O
inputs	O
of	O
paddles	B-Device
to	O
be	O
used	O
,	O
in	O
spite	O
of	O
the	O
port	O
already	O
handling	O
these	O
inputs	O
directly	O
meaning	O
all	O
that	O
was	O
needed	O
was	O
a	O
mechanical	O
adapter	O
.	O
</s>
<s>
The	O
ZX	B-Operating_System
Spectrum	I-Operating_System
prior	O
to	O
the	O
Spectrum	O
+2	O
had	O
no	O
built-in	O
controller	O
port	O
,	O
which	O
led	O
to	O
a	O
profusion	O
of	O
different	O
inputs	O
.	O
</s>
<s>
Atari	O
port	O
adapters	O
were	O
common	O
,	O
and	O
several	O
devices	O
emerged	O
including	O
the	O
Kempston	O
Interface	O
and	O
ZX	B-Device
Interface	I-Device
2	I-Device
that	O
were	O
incompatible	O
with	O
each	O
other	O
.	O
</s>
<s>
The	O
Interface	O
2	O
turned	O
joystick	O
presses	O
into	O
keyboard	O
presses	O
,	O
and	O
thus	O
could	O
not	O
generate	O
the	O
analog	O
signals	O
of	O
the	O
paddles	B-Device
.	O
</s>
<s>
The	O
later	O
Amstrad-built	O
Spectrum	O
models	O
-	O
the	O
+2	O
,	O
+2A	O
,	O
and	O
+3	O
-	O
included	O
two	O
built-in	O
joystick	B-Protocol
ports	I-Protocol
,	O
however	O
the	O
pinout	O
of	O
the	O
connectors	O
was	O
non-standard	O
.	O
</s>
<s>
The	O
BBC	B-Device
Micro	I-Device
had	O
a	O
relatively	O
complex	O
port	O
system	O
which	O
was	O
based	O
on	O
a	O
15-pin	O
D-connector	B-Protocol
that	O
supported	O
two	O
analog	O
joysticks	O
like	O
the	O
ones	O
on	O
the	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
These	O
ran	O
to	O
dedicated	O
analog-to-digital	O
circuitry	O
,	O
which	O
made	O
them	O
excellent	O
for	O
the	O
sort	O
of	O
interfacing	O
tasks	O
seen	O
in	O
(	O
for	O
instance	O
)	O
AtariLab	B-Application
.	O
</s>
<s>
( *	O
1	O
)	O
Atari	B-General_Concept
7800	I-General_Concept
buttons	O
require	O
special	O
wiring	O
.	O
</s>
<s>
The	O
Mega	B-Operating_System
Drive	I-Operating_System
controllers	O
use	O
an	O
active	O
circuit	O
.	O
</s>
<s>
( *	O
6	O
)	O
Refers	O
to	O
the	O
ports	O
built	O
into	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
+2	O
,	O
+2A	O
,	O
and	O
+3	O
models	O
.	O
</s>
<s>
( *	O
7	O
)	O
The	O
TI-99/4A	B-Device
and	O
Tutor/Pyuuta	O
controllers	O
were	O
typically	O
two	O
controllers	O
plugged	O
into	O
one	O
port	O
.	O
</s>
