<s>
A	O
PC	B-Device
speaker	I-Device
is	O
a	O
loudspeaker	O
built	O
into	O
some	O
IBM	B-Device
PC	I-Device
compatible	O
computers	O
.	O
</s>
<s>
The	O
first	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
,	O
model	O
5150	O
,	O
employed	O
a	O
standard	O
2.25inch	O
magnetic	O
driven	O
(	O
dynamic	O
)	O
speaker	O
.	O
</s>
<s>
More	O
recent	O
computers	O
use	O
a	O
tiny	O
moving-iron	B-Architecture
or	O
piezo	O
speaker	O
instead	O
.	O
</s>
<s>
The	O
speaker	O
allows	O
software	O
and	O
firmware	B-Application
to	O
provide	O
auditory	O
feedback	O
to	O
a	O
user	O
,	O
such	O
as	O
to	O
report	O
a	O
hardware	O
fault	O
.	O
</s>
<s>
A	O
PC	B-Device
speaker	I-Device
generates	O
waveforms	O
using	O
the	O
programmable	B-Device
interval	I-Device
timer	I-Device
,	O
an	O
Intel	B-Device
8253	I-Device
or	O
8254	B-Device
chip	O
.	O
</s>
<s>
The	O
PC	B-Device
speaker	I-Device
is	O
used	O
during	O
the	O
power-on	B-Device
self-test	I-Device
(	O
POST	O
)	O
sequence	O
to	O
indicate	O
errors	O
during	O
the	O
boot	B-Operating_System
process	I-Operating_System
.	O
</s>
<s>
Since	O
it	O
is	O
active	O
before	O
the	O
graphics	B-Device
card	I-Device
,	O
it	O
can	O
be	O
used	O
to	O
communicate	O
"	O
beep	B-Device
codes	I-Device
"	O
related	O
to	O
problems	O
that	O
prevent	O
the	O
much	O
more	O
complex	O
initialization	O
of	O
the	O
graphics	B-Device
card	I-Device
to	O
take	O
place	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Video	B-Device
BIOS	I-Device
usually	O
cannot	O
activate	O
a	O
graphics	B-Device
card	I-Device
unless	O
working	O
RAM	O
is	O
present	O
in	O
the	O
system	O
while	O
beeping	O
the	O
speaker	O
is	O
possible	O
with	O
just	O
ROM	O
and	O
the	O
CPU	O
registers	O
.	O
</s>
<s>
These	O
patterns	O
are	O
specific	O
to	O
the	O
BIOS/UEFI	O
manufacturer	O
and	O
are	O
usually	O
documented	O
in	O
the	O
technical	O
manual	O
of	O
the	O
motherboard	B-Device
.	O
</s>
<s>
Several	O
programs	O
,	O
including	O
music	O
software	O
,	O
operating	O
systems	O
or	O
games	O
,	O
could	O
play	O
pulse-code	B-Algorithm
modulation	I-Algorithm
(	O
PCM	B-Algorithm
)	O
sound	O
through	O
the	O
PC	B-Device
speaker	I-Device
using	O
special	O
Pulse-width	B-Algorithm
Modulation	I-Algorithm
techniques	O
explained	O
later	O
in	O
this	O
article	O
.	O
</s>
<s>
The	O
PC	B-Device
speaker	I-Device
was	O
often	O
used	O
in	O
very	O
innovative	O
ways	O
to	O
create	O
the	O
impression	O
of	O
polyphonic	O
music	O
or	O
sound	O
effects	O
within	O
computer	O
games	O
of	O
its	O
era	O
,	O
such	O
as	O
the	O
LucasArts	O
series	O
of	O
adventure	O
games	O
from	O
the	O
mid-1980s	O
,	O
using	O
swift	O
arpeggios	O
.	O
</s>
<s>
Several	O
games	O
such	O
as	O
Space	B-Application
Hulk	I-Application
and	O
Pinball	B-Application
Fantasies	I-Application
were	O
noted	O
for	O
their	O
elaborate	O
sound	O
effects	O
;	O
Space	B-Application
Hulk	I-Application
,	O
in	O
particular	O
,	O
even	O
had	O
full	O
speech	O
.	O
</s>
<s>
However	O
,	O
because	O
the	O
method	O
used	O
to	O
reproduce	O
PCM	B-Algorithm
was	O
very	O
sensitive	O
to	O
timing	O
issues	O
,	O
these	O
effects	O
either	O
caused	O
noticeable	O
sluggishness	O
on	O
slower	O
PCs	O
or	O
sometimes	O
failed	O
on	O
faster	O
PCs	O
(	O
that	O
is	O
,	O
significantly	O
faster	O
than	O
the	O
program	O
was	O
originally	O
developed	O
for	O
)	O
.	O
</s>
<s>
Thus	O
,	O
when	O
sound	B-Device
cards	I-Device
(	O
which	O
can	O
output	O
complex	O
sounds	O
independent	O
from	O
the	O
CPU	O
once	O
initiated	O
)	O
became	O
mainstream	O
in	O
the	O
PC	O
market	O
after	O
1990	O
,	O
they	O
quickly	O
replaced	O
the	O
PC	B-Device
speaker	I-Device
as	O
the	O
preferred	O
output	O
device	O
for	O
sound	O
effects	O
.	O
</s>
<s>
Several	O
programs	O
,	O
including	O
MP	O
(	O
Module	O
Player	O
,	O
1989	O
)	O
,	O
Scream	B-Application
Tracker	I-Application
,	O
Fast	O
Tracker	O
,	O
Impulse	B-Application
Tracker	I-Application
,	O
and	O
even	O
device	B-Application
drivers	I-Application
for	O
Linux	B-Application
and	O
Microsoft	B-Application
Windows	I-Application
,	O
could	O
play	O
PCM	B-Algorithm
sound	O
through	O
the	O
PC	B-Device
speaker	I-Device
.	O
</s>
<s>
Modern	O
Microsoft	B-Application
Windows	I-Application
systems	O
have	O
PC	B-Device
speaker	I-Device
support	O
as	O
a	O
separate	O
device	O
with	O
special	O
capabilities	O
–	O
that	O
is	O
,	O
it	O
cannot	O
be	O
configured	O
as	O
a	O
normal	O
audio	O
output	O
device	O
.	O
</s>
<s>
For	O
example	O
,	O
Skype	B-Application
can	O
use	O
it	O
as	O
a	O
reserve	O
calling	O
signal	O
device	O
for	O
the	O
case	O
where	O
the	O
primary	O
audio	O
output	O
device	O
cannot	O
be	O
heard	O
(	O
for	O
example	O
because	O
the	O
volume	O
is	O
set	O
to	O
the	O
minimum	O
level	O
or	O
the	O
amplifier	O
is	O
turned	O
off	O
)	O
.	O
</s>
<s>
In	O
the	O
1990s	O
,	O
a	O
computer	O
virus	O
for	O
Microsoft	B-Application
DOS	I-Application
named	O
"	O
Techno	O
"	O
appeared	O
,	O
playing	O
a	O
melody	O
through	O
the	O
PC	B-Device
speaker	I-Device
while	O
printing	O
the	O
word	O
"	O
TECHNO	O
"	O
on	O
the	O
screen	O
until	O
filled	O
.	O
</s>
<s>
In	O
some	O
applications	O
,	O
the	O
PC	B-Device
speaker	I-Device
is	O
affixed	O
directly	O
to	O
the	O
computer	O
's	O
motherboard	B-Device
;	O
in	O
others	O
,	O
including	O
the	O
first	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
,	O
the	O
speaker	O
is	O
attached	O
by	O
wire	O
to	O
a	O
connector	O
on	O
the	O
motherboard	B-Device
.	O
</s>
<s>
Some	O
PC	O
cases	O
come	O
with	O
a	O
PC	B-Device
speaker	I-Device
preinstalled	O
.	O
</s>
<s>
A	O
wired	O
PC	B-Device
speaker	I-Device
connector	O
may	O
have	O
a	O
two-	O
,	O
three-	O
,	O
or	O
four-pin	O
configuration	O
,	O
and	O
either	O
two	O
or	O
three	O
wires	O
.	O
</s>
<s>
The	O
female	O
connector	O
of	O
the	O
speaker	O
connects	O
to	O
pin	B-Protocol
headers	I-Protocol
on	O
the	O
motherboard	B-Device
,	O
which	O
are	O
sometimes	O
labeled	O
or	O
.	O
</s>
<s>
The	O
PC	B-Device
speaker	I-Device
is	O
normally	O
meant	O
to	O
reproduce	O
a	O
square	O
wave	O
via	O
only	O
2	O
levels	O
of	O
output	O
(	O
two	O
voltage	O
levels	O
,	O
typically	O
0V	O
and	O
5V	O
)	O
,	O
driven	O
by	O
channel	O
2	O
of	O
the	O
Intel	B-Device
8253	I-Device
(	O
PC	O
,	O
XT	O
)	O
or	O
8254	B-Device
(	O
AT	O
and	O
later	O
)	O
Programmable	B-Device
Interval	I-Device
Timer	I-Device
operating	O
in	O
mode	O
three	O
(	O
square	O
wave	O
signal	O
)	O
.	O
</s>
<s>
However	O
,	O
by	O
carefully	O
timing	O
a	O
short	O
pulse	B-Algorithm
(	O
i.e.	O
</s>
<s>
This	O
technique	O
is	O
called	O
pulse-width	B-Algorithm
modulation	I-Algorithm
(	O
PWM	O
)	O
and	O
allows	O
approximate	O
playback	O
of	O
PCM	B-Algorithm
audio	I-Algorithm
.	O
</s>
<s>
With	O
the	O
PC	B-Device
speaker	I-Device
this	O
method	O
achieves	O
limited	O
quality	O
playback	O
,	O
but	O
a	O
commercial	O
solution	O
named	O
RealSound	O
used	O
it	O
to	O
provide	O
improved	O
sound	O
on	O
several	O
games	O
.	O
</s>
<s>
On	O
the	O
PC	B-Device
speaker	I-Device
,	O
however	O
,	O
the	O
output	O
voltage	O
is	O
either	O
zero	O
or	O
TTL	B-General_Concept
level	O
(	O
unipolar	O
)	O
.	O
</s>
<s>
The	O
clock	O
rate	O
of	O
the	O
PC	O
's	O
programmable	B-Device
interval	I-Device
timer	I-Device
which	O
drives	O
the	O
speaker	O
is	O
fixed	O
at	O
1,193,180	O
Hz	O
,	O
and	O
the	O
product	O
of	O
the	O
audio	O
sample	O
rate	O
times	O
the	O
maximum	O
DAC	O
value	O
must	O
equal	O
this	O
.	O
</s>
<s>
The	O
audio	O
fidelity	O
of	O
this	O
technique	O
is	O
further	O
decreased	O
by	O
the	O
lack	O
of	O
a	O
properly	O
sized	O
dynamic	O
loudspeaker	O
,	O
specially	O
in	O
modern	O
machines	O
and	O
particularly	O
laptops	O
that	O
use	O
a	O
tiny	O
moving-iron	B-Architecture
speaker	O
(	O
often	O
confused	O
with	O
piezoelectric	O
)	O
.	O
</s>
<s>
A	O
normal	O
dynamic	O
loudspeaker	O
does	O
this	O
naturally	O
,	O
but	O
the	O
tiny	O
metal	O
diaphragm	O
of	O
the	O
moving-iron	B-Architecture
speaker	O
will	O
let	O
much	O
switching	O
noise	O
pass	O
,	O
as	O
will	O
many	O
direct	O
couplings	O
(	O
though	O
there	O
are	O
exceptions	O
to	O
this	O
,	O
e.g.	O
</s>
<s>
filtered	O
"	O
speaker	O
in	O
"	O
ports	O
on	O
some	O
motherboards	B-Device
and	O
sound	B-Device
cards	I-Device
)	O
.	O
</s>
<s>
This	O
use	O
of	O
the	O
PC	B-Device
speaker	I-Device
for	O
complex	O
audio	O
output	O
became	O
less	O
common	O
with	O
the	O
introduction	O
of	O
Sound	B-Application
Blaster	I-Application
and	O
other	O
sound	B-Device
cards	I-Device
.	O
</s>
