<s>
In	O
computing	O
,	O
an	O
expansion	B-Device
card	I-Device
(	O
also	O
called	O
an	O
expansion	B-Device
board	I-Device
,	O
adapter	B-Device
card	I-Device
,	O
peripheral	O
card	O
or	O
accessory	B-Device
card	I-Device
)	O
is	O
a	O
printed	O
circuit	O
board	O
that	O
can	O
be	O
inserted	O
into	O
an	O
electrical	B-Protocol
connector	I-Protocol
,	O
or	O
expansion	B-Device
slot	I-Device
(	O
also	O
referred	O
to	O
as	O
a	O
bus	B-General_Concept
slot	O
)	O
on	O
a	O
computer	O
's	O
motherboard	B-Device
(	O
see	O
also	O
backplane	B-Architecture
)	O
to	O
add	O
functionality	O
to	O
a	O
computer	O
system	O
.	O
</s>
<s>
Sometimes	O
the	O
design	O
of	O
the	O
computer	O
's	O
case	B-General_Concept
and	O
motherboard	B-Device
involves	O
placing	O
most	O
(	O
or	O
all	O
)	O
of	O
these	O
slots	O
onto	O
a	O
separate	O
,	O
removable	O
card	O
.	O
</s>
<s>
Typically	O
such	O
cards	O
are	O
referred	O
to	O
as	O
a	O
riser	B-Architecture
card	I-Architecture
in	O
part	O
because	O
they	O
project	O
upward	O
from	O
the	O
board	O
and	O
allow	O
expansion	B-Device
cards	I-Device
to	O
be	O
placed	O
above	O
and	O
parallel	O
to	O
the	O
motherboard	B-Device
.	O
</s>
<s>
Expansion	B-Device
cards	I-Device
allow	O
the	O
capabilities	O
and	O
interfaces	O
of	O
a	O
computer	O
system	O
to	O
be	O
extended	O
or	O
supplemented	O
in	O
a	O
way	O
appropriate	O
to	O
the	O
tasks	O
it	O
will	O
perform	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
high-speed	O
multi-channel	O
data	O
acquisition	O
system	O
would	O
be	O
of	O
no	O
use	O
in	O
a	O
personal	B-Device
computer	I-Device
used	O
for	O
bookkeeping	O
,	O
but	O
might	O
be	O
a	O
key	O
part	O
of	O
a	O
system	O
used	O
for	O
industrial	O
process	O
control	O
.	O
</s>
<s>
Expansion	B-Device
cards	I-Device
can	O
often	O
be	O
installed	O
or	O
removed	O
in	O
the	O
field	O
,	O
allowing	O
a	O
degree	O
of	O
user	O
customization	O
for	O
particular	O
purposes	O
.	O
</s>
<s>
Some	O
expansion	B-Device
cards	I-Device
take	O
the	O
form	O
of	O
"	O
daughterboards	O
"	O
that	O
plug	O
into	O
connectors	O
on	O
a	O
supporting	O
system	B-Device
board	I-Device
.	O
</s>
<s>
In	O
personal	B-Device
computing	I-Device
,	O
notable	O
expansion	O
buses	O
and	O
expansion	B-Device
card	I-Device
standards	O
include	O
the	O
S-100	B-Architecture
bus	I-Architecture
from	O
1974	O
associated	O
with	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
,	O
the	O
50-pin	O
expansion	B-Device
slots	I-Device
of	O
the	O
original	O
Apple	B-Device
II	I-Device
computer	O
from	O
1977	O
(	O
unique	O
to	O
Apple	O
)	O
,	O
IBM	O
's	O
Industry	B-Architecture
Standard	I-Architecture
Architecture	I-Architecture
(	O
ISA	B-Architecture
)	O
introduced	O
with	O
the	O
IBM	B-Device
PC	I-Device
in	O
1981	O
,	O
Acorn	O
's	O
tube	B-Device
expansion	I-Device
bus	I-Device
on	O
the	O
BBC	B-Device
Micro	I-Device
also	O
from	O
1981	O
,	O
IBM	O
's	O
patented	O
and	O
proprietary	O
Micro	B-Device
Channel	I-Device
architecture	I-Device
(	O
MCA	B-Device
)	O
from	O
1987	O
that	O
never	O
won	O
favour	O
in	O
the	O
clone	O
market	O
,	O
the	O
vastly	O
improved	O
Peripheral	B-Protocol
Component	I-Protocol
Interconnect	I-Protocol
(	O
PCI	B-Protocol
)	O
that	O
displaced	O
ISA	B-Architecture
in	O
1992	O
,	O
and	O
PCI	B-Protocol
Express	O
from	O
2003	O
which	O
abstracts	O
the	O
interconnect	B-General_Concept
into	O
high-speed	O
communication	O
"	O
lanes	O
"	O
and	O
relegates	O
all	O
other	O
functions	O
into	O
software	O
protocol	O
.	O
</s>
<s>
Processor	O
,	O
memory	O
and	O
I/O	B-Device
cards	I-Device
became	O
feasible	O
with	O
the	O
development	O
of	O
integrated	O
circuits	O
.	O
</s>
<s>
Expansion	B-Device
cards	I-Device
make	O
processor	O
systems	O
adaptable	O
to	O
the	O
needs	O
of	O
the	O
user	O
by	O
making	O
it	O
possible	O
to	O
connect	O
various	O
types	O
of	O
devices	O
,	O
including	O
I/O	B-General_Concept
,	O
additional	O
memory	O
,	O
and	O
optional	O
features	O
(	O
such	O
as	O
a	O
floating	B-General_Concept
point	I-General_Concept
unit	I-General_Concept
)	O
to	O
the	O
central	O
processor	O
.	O
</s>
<s>
Minicomputers	O
,	O
starting	O
with	O
the	O
PDP-8	B-Device
,	O
were	O
made	O
of	O
multiple	O
cards	O
communicating	O
through	O
,	O
and	O
powered	O
by	O
,	O
a	O
passive	B-Architecture
backplane	I-Architecture
.	O
</s>
<s>
The	O
first	O
commercial	O
microcomputer	B-Architecture
to	O
feature	O
expansion	B-Device
slots	I-Device
was	O
the	O
Micral	B-Device
N	I-Device
,	O
in	O
1973	O
.	O
</s>
<s>
The	O
first	O
company	O
to	O
establish	O
a	O
de	O
facto	O
standard	O
was	O
Altair	O
with	O
the	O
Altair	B-Architecture
8800	I-Architecture
,	O
developed	O
1974	O
–	O
1975	O
,	O
which	O
later	O
became	O
a	O
multi-manufacturer	O
standard	O
,	O
the	O
S-100	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
Many	O
of	O
these	O
computers	O
were	O
also	O
passive	B-Architecture
backplane	I-Architecture
designs	O
,	O
where	O
all	O
elements	O
of	O
the	O
computer	O
,	O
(	O
processor	O
,	O
memory	O
,	O
and	O
I/O	B-General_Concept
)	O
plugged	O
into	O
a	O
card	O
cage	O
which	O
passively	O
distributed	O
signals	O
and	O
power	O
between	O
the	O
cards	O
.	O
</s>
<s>
Proprietary	O
bus	B-General_Concept
implementations	O
for	O
systems	O
such	O
as	O
the	O
Apple	B-Device
II	I-Device
co-existed	O
with	O
multi-manufacturer	O
standards	O
.	O
</s>
<s>
IBM	O
introduced	O
what	O
would	O
retroactively	O
be	O
called	O
the	O
Industry	B-Architecture
Standard	I-Architecture
Architecture	I-Architecture
(	O
ISA	B-Architecture
)	O
bus	B-General_Concept
with	O
the	O
IBM	B-Device
PC	I-Device
in	O
1981	O
.	O
</s>
<s>
At	O
that	O
time	O
,	O
the	O
technology	O
was	O
called	O
the	O
PC	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
The	O
IBM	B-Device
XT	I-Device
,	O
introduced	O
in	O
1983	O
,	O
used	O
the	O
same	O
bus	B-General_Concept
(	O
with	O
slight	O
exception	O
)	O
.	O
</s>
<s>
The	O
8-bit	O
PC	O
and	O
XT	B-Architecture
bus	I-Architecture
was	O
extended	O
with	O
the	O
introduction	O
of	O
the	O
IBM	O
AT	O
in	O
1984	O
.	O
</s>
<s>
This	O
used	O
a	O
second	O
connector	O
for	O
extending	O
the	O
address	O
and	O
data	B-General_Concept
bus	I-General_Concept
over	O
the	O
XT	O
,	O
but	O
was	O
backward	O
compatible	O
;	O
8-bit	O
cards	O
were	O
still	O
usable	O
in	O
the	O
AT	O
16-bit	O
slots	O
.	O
</s>
<s>
Industry	B-Architecture
Standard	I-Architecture
Architecture	I-Architecture
(	O
ISA	B-Architecture
)	O
became	O
the	O
designation	O
for	O
the	O
IBM	O
AT	B-Architecture
bus	I-Architecture
after	O
other	O
types	O
were	O
developed	O
.	O
</s>
<s>
Users	O
of	O
the	O
ISA	B-Architecture
bus	I-Architecture
had	O
to	O
have	O
in-depth	O
knowledge	O
of	O
the	O
hardware	O
they	O
were	O
adding	O
to	O
properly	O
connect	O
the	O
devices	O
,	O
since	O
memory	O
addresses	O
,	O
I/O	B-General_Concept
port	O
addresses	O
,	O
and	O
DMA	B-General_Concept
channels	O
had	O
to	O
be	O
configured	O
by	O
switches	O
or	O
jumpers	O
on	O
the	O
card	O
to	O
match	O
the	O
settings	O
in	O
driver	O
software	O
.	O
</s>
<s>
IBM	O
's	O
MCA	B-Device
bus	I-Device
,	O
developed	O
for	O
the	O
PS/2	O
in	O
1987	O
,	O
was	O
a	O
competitor	O
to	O
ISA	B-Architecture
,	O
also	O
their	O
design	O
,	O
but	O
fell	O
out	O
of	O
favor	O
due	O
to	O
the	O
ISA	B-Architecture
's	O
industry-wide	O
acceptance	O
and	O
IBM	O
's	O
licensing	O
of	O
MCA	B-Device
.	O
</s>
<s>
EISA	O
,	O
the	O
32-bit	O
extended	O
version	O
of	O
ISA	B-Architecture
championed	O
by	O
Compaq	O
,	O
was	O
used	O
on	O
some	O
PC	B-Device
motherboards	I-Device
until	O
1997	O
,	O
when	O
Microsoft	O
declared	O
it	O
a	O
"	O
legacy	B-Device
"	O
subsystem	O
in	O
the	O
PC	O
97	O
industry	O
white-paper	O
.	O
</s>
<s>
Compaq	O
)	O
and	O
then	O
the	O
VESA	O
Local	O
Bus	B-General_Concept
Standard	O
,	O
were	O
late	O
1980s	O
expansion	O
buses	O
that	O
were	O
tied	O
but	O
not	O
exclusive	O
to	O
the	O
80386	O
and	O
80486	O
CPU	B-General_Concept
bus	B-General_Concept
.	O
</s>
<s>
The	O
PC/104	B-Device
bus	B-General_Concept
is	O
an	O
embedded	O
bus	B-General_Concept
that	O
copies	O
the	O
ISA	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
Intel	O
launched	O
their	O
PCI	B-Protocol
bus	I-Protocol
chipsets	O
along	O
with	O
the	O
P5-based	O
Pentium	B-Device
CPUs	O
in	O
1993	O
.	O
</s>
<s>
The	O
PCI	B-Protocol
bus	I-Protocol
was	O
introduced	O
in	O
1991	O
as	O
a	O
replacement	O
for	O
ISA	B-Architecture
.	O
</s>
<s>
The	O
standard	O
(	O
now	O
at	O
version	O
3.0	O
)	O
is	O
found	O
on	O
PC	B-Device
motherboards	I-Device
to	O
this	O
day	O
.	O
</s>
<s>
The	O
PCI	B-Protocol
standard	O
supports	O
bus	B-General_Concept
bridging	O
:	O
as	O
many	O
as	O
ten	O
daisy	O
chained	O
PCI	B-Protocol
buses	O
have	O
been	O
tested	O
.	O
</s>
<s>
Cardbus	O
,	O
using	O
the	O
PCMCIA	B-Architecture
connector	O
,	O
is	O
a	O
PCI	B-Protocol
format	O
that	O
attaches	O
peripherals	O
to	O
the	O
Host	O
PCI	B-Protocol
Bus	I-Protocol
via	O
PCI	B-Protocol
to	O
PCI	B-Protocol
Bridge	I-Protocol
.	O
</s>
<s>
Cardbus	O
is	O
being	O
supplanted	O
by	O
ExpressCard	B-Device
format	O
.	O
</s>
<s>
Intel	O
introduced	O
the	O
AGP	B-Architecture
bus	B-General_Concept
in	O
1997	O
as	O
a	O
dedicated	O
video	O
acceleration	O
solution	O
.	O
</s>
<s>
AGP	B-Architecture
devices	O
are	O
logically	O
attached	O
to	O
the	O
PCI	B-Protocol
bus	I-Protocol
over	O
a	O
PCI-to-PCI	O
bridge	O
.	O
</s>
<s>
Though	O
termed	O
a	O
bus	B-General_Concept
,	O
AGP	B-Architecture
usually	O
supports	O
only	O
a	O
single	O
card	O
at	O
a	O
time	O
(	O
Legacy	B-Operating_System
BIOS	I-Operating_System
support	O
issues	O
)	O
.	O
</s>
<s>
From	O
2005	O
PCI	B-Protocol
Express	O
has	O
been	O
replacing	O
both	O
PCI	B-Protocol
and	O
AGP	B-Architecture
.	O
</s>
<s>
This	O
standard	O
,	O
approved	O
in	O
2004	O
,	O
implements	O
the	O
logical	O
PCI	B-Protocol
protocol	O
over	O
a	O
serial	O
communication	O
interface	O
.	O
</s>
<s>
PC/104	B-Device
(	O
-Plus	O
)	O
or	O
Mini	O
PCI	B-Protocol
are	O
often	O
added	O
for	O
expansion	O
on	O
small	O
form	O
factor	O
boards	O
such	O
as	O
Mini-ITX	B-Architecture
.	O
</s>
<s>
For	O
their	O
1000	O
EX	O
and	O
1000	O
HX	O
models	O
,	O
Tandy	O
Computer	O
designed	O
the	O
PLUS	O
expansion	O
interface	O
,	O
an	O
adaptation	O
of	O
the	O
XT-bus	O
supporting	O
cards	O
of	O
a	O
smaller	O
form	O
factor	O
.	O
</s>
<s>
Because	O
it	O
is	O
electrically	O
compatible	O
with	O
the	O
XT	B-Architecture
bus	I-Architecture
(	O
a.k.a.	O
</s>
<s>
8-bit	O
ISA	B-Architecture
or	O
XT-ISA	O
)	O
,	O
a	O
passive	O
adapter	O
can	O
be	O
made	O
to	O
connect	O
XT	O
cards	O
to	O
a	O
PLUS	O
expansion	O
connector	O
.	O
</s>
<s>
Another	O
bus	B-General_Concept
that	O
offered	O
stackable	O
expansion	O
modules	O
was	O
the	O
"	O
sidecar	O
"	O
bus	B-General_Concept
used	O
by	O
the	O
IBM	B-Device
PCjr	I-Device
.	O
</s>
<s>
This	O
may	O
have	O
been	O
electrically	O
comparable	O
to	O
the	O
XT	B-Architecture
bus	I-Architecture
;	O
it	O
most	O
certainly	O
had	O
some	O
similarities	O
since	O
both	O
essentially	O
exposed	O
the	O
8088	O
CPU	B-General_Concept
's	O
address	O
and	O
data	B-General_Concept
buses	I-General_Concept
,	O
with	O
some	O
buffering	O
and	O
latching	O
,	O
the	O
addition	O
of	O
interrupts	B-Application
and	O
DMA	B-General_Concept
provided	O
by	O
Intel	O
add-on	O
chips	O
,	O
and	O
a	O
few	O
system	O
fault	B-General_Concept
detection	O
lines	O
(	O
Power	O
Good	O
,	O
Memory	O
Check	O
,	O
I/O	B-General_Concept
Channel	O
Check	O
)	O
.	O
</s>
<s>
Again	O
,	O
PCjr	B-Device
sidecars	O
are	O
not	O
technically	O
expansion	B-Device
cards	I-Device
,	O
but	O
expansion	O
modules	O
,	O
with	O
the	O
only	O
difference	O
being	O
that	O
the	O
sidecar	O
is	O
an	O
expansion	B-Device
card	I-Device
enclosed	O
in	O
a	O
plastic	O
box	O
(	O
with	O
holes	O
exposing	O
the	O
connectors	O
)	O
.	O
</s>
<s>
Laptops	O
are	O
generally	O
unable	O
to	O
accept	O
most	O
expansion	B-Device
cards	I-Device
intended	O
for	O
desktop	O
computers	O
.	O
</s>
<s>
The	O
original	O
PC	B-Architecture
Card	I-Architecture
expansion	B-Device
card	I-Device
standard	O
is	O
essentially	O
a	O
compact	O
version	O
of	O
the	O
ISA	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
The	O
CardBus	O
expansion	B-Device
card	I-Device
standard	O
is	O
an	O
evolution	O
of	O
the	O
PC	B-Architecture
card	I-Architecture
standard	O
to	O
make	O
it	O
into	O
a	O
compact	O
version	O
of	O
the	O
PCI	B-Protocol
bus	I-Protocol
.	O
</s>
<s>
The	O
original	O
ExpressCard	B-Device
standard	O
acts	O
like	O
it	O
is	O
either	O
a	O
USB	O
2.0	O
peripheral	O
or	O
a	O
PCI	B-Protocol
Express	O
1.x	O
x1	O
device	O
.	O
</s>
<s>
ExpressCard	B-Device
2.0	O
adds	O
SuperSpeed	O
USB	O
as	O
another	O
type	O
of	O
interface	O
the	O
card	O
can	O
use	O
.	O
</s>
<s>
Unfortunately	O
,	O
CardBus	O
and	O
ExpressCard	B-Device
are	O
vulnerable	O
to	O
DMA	B-General_Concept
attack	O
unless	O
the	O
laptop	O
has	O
an	O
IOMMU	O
that	O
is	O
configured	O
to	O
thwart	O
these	O
attacks	O
.	O
</s>
<s>
The	O
most	O
well	O
known	O
examples	O
are	O
Mini-PCI	O
or	O
Mini	O
PCIe	O
.	O
</s>
<s>
Such	O
slots	O
were	O
usually	O
intended	O
for	O
a	O
specific	O
purpose	O
such	O
as	O
offering	O
"	O
built-in	O
"	O
wireless	O
networking	O
or	O
upgrading	O
the	O
system	O
at	O
production	O
with	O
a	O
discrete	B-Device
GPU	I-Device
.	O
</s>
<s>
Most	O
other	O
computer	O
lines	O
,	O
including	O
those	O
from	O
Apple	O
Inc	O
.	O
such	O
as	O
the	O
(	O
Apple	B-Device
II	I-Device
and	O
Macintosh	B-Device
)	O
,	O
Tandy	O
,	O
Commodore	O
,	O
Amiga	B-Device
,	O
and	O
Atari	O
,	O
offered	O
their	O
own	O
expansion	O
buses	O
.	O
</s>
<s>
The	O
Amiga	B-Device
used	O
Zorro	B-Device
II	I-Device
.	O
</s>
<s>
Apple	O
used	O
a	O
proprietary	O
system	O
with	O
seven	O
50-pin-slots	O
for	O
Apple	B-Device
II	I-Device
peripheral	O
cards	O
,	O
then	O
later	O
used	O
both	O
variations	O
on	O
Processor	B-Device
Direct	I-Device
Slot	I-Device
and	O
NuBus	B-Device
for	O
its	O
Macintosh	B-Device
series	O
until	O
1995	O
,	O
when	O
they	O
switched	O
to	O
a	O
PCI	B-Protocol
Bus	I-Protocol
.	O
</s>
<s>
Generally	O
speaking	O
,	O
most	O
PCI	B-Protocol
expansion	B-Device
cards	I-Device
will	O
function	O
on	O
any	O
CPU	B-General_Concept
platform	O
which	O
incorporates	O
PCI	B-Protocol
bus	I-Protocol
hardware	O
provided	O
there	O
is	O
a	O
software	O
driver	O
for	O
that	O
type	O
.	O
</s>
<s>
PCI	B-Protocol
video	B-Device
cards	I-Device
and	O
any	O
other	O
cards	O
that	O
contain	O
their	O
own	O
BIOS	B-Operating_System
or	O
other	O
ROM	O
are	O
problematic	O
,	O
although	O
video	B-Device
cards	I-Device
conforming	O
to	O
VESA	O
Standards	O
may	O
be	O
used	O
for	O
secondary	O
monitors	O
.	O
</s>
<s>
DEC	O
Alpha	O
,	O
IBM	O
PowerPC	O
,	O
and	O
NEC	O
MIPS	O
workstations	O
used	O
PCI	B-Protocol
bus	I-Protocol
connectors	O
.	O
</s>
<s>
Both	O
Zorro	B-Device
II	I-Device
and	O
NuBus	B-Device
were	O
plug	B-Device
and	I-Device
play	I-Device
,	O
requiring	O
no	O
hardware	O
configuration	O
by	O
the	O
user	O
.	O
</s>
<s>
Other	O
computer	B-General_Concept
buses	I-General_Concept
were	O
used	O
for	O
industrial	O
control	O
,	O
instruments	O
,	O
and	O
scientific	O
systems	O
.	O
</s>
<s>
One	O
specific	O
example	O
is	O
HP-IB	O
(	O
or	O
Hewlett	O
Packard	O
Interface	O
Bus	B-General_Concept
)	O
which	O
was	O
ultimately	O
standardized	O
as	O
IEEE-488	O
(	O
aka	O
GPIB	O
)	O
.	O
</s>
<s>
Some	O
well-known	O
historical	O
standards	O
include	O
VMEbus	B-Architecture
,	O
STD	B-Architecture
Bus	I-Architecture
,	O
SBus	B-Architecture
(	O
specific	O
to	O
Sun	O
's	O
SPARCStations	O
)	O
,	O
and	O
numerous	O
others	O
.	O
</s>
<s>
Many	O
other	O
video	B-Device
game	I-Device
consoles	I-Device
such	O
as	O
the	O
Nintendo	O
Entertainment	O
System	O
and	O
the	O
Sega	B-Operating_System
Genesis	I-Operating_System
included	O
expansion	O
buses	O
in	O
some	O
form	O
;	O
In	O
the	O
case	B-General_Concept
of	O
at	O
least	O
the	O
Genesis	O
,	O
the	O
expansion	B-Device
bus	I-Device
was	O
proprietary	O
.	O
</s>
<s>
In	O
fact	O
,	O
the	O
cartridge	O
slots	O
of	O
many	O
cartridge-based	O
consoles	O
(	O
not	O
counting	O
the	O
Atari	B-General_Concept
2600	I-General_Concept
)	O
would	O
qualify	O
as	O
expansion	O
buses	O
,	O
as	O
they	O
exposed	O
both	O
read	O
and	O
write	O
capabilities	O
of	O
the	O
system	O
's	O
internal	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
However	O
,	O
the	O
expansion	O
modules	O
attached	O
to	O
these	O
interfaces	O
,	O
though	O
functionally	O
the	O
same	O
as	O
expansion	B-Device
cards	I-Device
,	O
are	O
not	O
technically	O
expansion	B-Device
cards	I-Device
,	O
due	O
to	O
their	O
physical	O
form	O
.	O
</s>
<s>
The	O
primary	O
purpose	O
of	O
an	O
expansion	B-Device
card	I-Device
is	O
to	O
provide	O
or	O
expand	O
on	O
features	O
not	O
offered	O
by	O
the	O
motherboard	B-Device
.	O
</s>
<s>
For	O
example	O
,	O
the	O
original	O
IBM	B-Device
PC	I-Device
did	O
not	O
have	O
on-board	O
graphics	O
or	O
hard	O
drive	O
capability	O
.	O
</s>
<s>
In	O
that	O
case	B-General_Concept
,	O
a	O
graphics	B-Device
card	I-Device
and	O
an	O
ST-506	B-Device
hard	O
disk	O
controller	O
card	O
provided	O
graphics	O
capability	O
and	O
hard	O
drive	O
interface	O
respectively	O
.	O
</s>
<s>
Some	O
single-board	B-Device
computers	I-Device
made	O
no	O
provision	O
for	O
expansion	B-Device
cards	I-Device
,	O
and	O
may	O
only	O
have	O
provided	O
IC	O
sockets	O
on	O
the	O
board	O
for	O
limited	O
changes	O
or	O
customization	O
.	O
</s>
<s>
Since	O
reliable	O
multi-pin	O
connectors	O
are	O
relatively	O
costly	O
,	O
some	O
mass-market	O
systems	O
such	O
as	O
home	O
computers	O
had	O
no	O
expansion	B-Device
slots	I-Device
and	O
instead	O
used	O
a	O
card-edge	O
connector	O
at	O
the	O
edge	O
of	O
the	O
main	B-Device
board	I-Device
,	O
putting	O
the	O
costly	O
matching	O
socket	O
into	O
the	O
cost	O
of	O
the	O
peripheral	O
device	O
.	O
</s>
<s>
In	O
the	O
case	B-General_Concept
of	O
expansion	O
of	O
on-board	O
capability	O
,	O
a	O
motherboard	B-Device
may	O
provide	O
a	O
single	B-Protocol
serial	I-Protocol
RS232	I-Protocol
port	I-Protocol
or	O
Ethernet	O
port	O
.	O
</s>
<s>
An	O
expansion	B-Device
card	I-Device
can	O
be	O
installed	O
to	O
offer	O
multiple	O
RS232	O
ports	O
or	O
multiple	O
and	O
higher	O
bandwidth	O
Ethernet	O
ports	O
.	O
</s>
<s>
In	O
this	O
case	B-General_Concept
,	O
the	O
motherboard	B-Device
provides	O
basic	O
functionality	O
but	O
the	O
expansion	B-Device
card	I-Device
offers	O
additional	O
or	O
enhanced	O
ports	O
.	O
</s>
<s>
One	O
edge	O
of	O
the	O
expansion	B-Device
card	I-Device
holds	O
the	O
contacts	O
(	O
the	O
edge	O
connector	O
or	O
pin	B-Protocol
header	I-Protocol
)	O
that	O
fit	O
into	O
the	O
slot	O
.	O
</s>
<s>
They	O
establish	O
the	O
electrical	O
contact	O
between	O
the	O
electronics	O
on	O
the	O
card	O
and	O
on	O
the	O
motherboard	B-Device
.	O
</s>
<s>
Peripheral	O
expansion	B-Device
cards	I-Device
generally	O
have	O
connectors	O
for	O
external	O
cables	O
.	O
</s>
<s>
In	O
the	O
PC-compatible	O
personal	B-Device
computer	I-Device
,	O
these	O
connectors	O
were	O
located	O
in	O
the	O
support	O
bracket	O
at	O
the	O
back	O
of	O
the	O
cabinet	O
.	O
</s>
<s>
Industrial	O
backplane	B-Architecture
systems	I-Architecture
had	O
connectors	O
mounted	O
on	O
the	O
top	O
edge	O
of	O
the	O
card	O
,	O
opposite	O
to	O
the	O
backplane	B-Architecture
pins	O
.	O
</s>
<s>
Depending	O
on	O
the	O
form	O
factor	O
of	O
the	O
motherboard	B-Device
and	O
case	B-General_Concept
,	O
around	O
one	O
to	O
seven	O
expansion	B-Device
cards	I-Device
can	O
be	O
added	O
to	O
a	O
computer	O
system	O
.	O
</s>
<s>
19	O
or	O
more	O
expansion	B-Device
cards	I-Device
can	O
be	O
installed	O
in	O
backplane	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
When	O
many	O
expansion	B-Device
cards	I-Device
are	O
added	O
to	O
a	O
system	O
,	O
total	O
power	O
consumption	O
and	O
heat	O
dissipation	O
become	O
limiting	O
factors	O
.	O
</s>
<s>
Some	O
expansion	B-Device
cards	I-Device
take	O
up	O
more	O
than	O
one	O
slot	O
space	O
.	O
</s>
<s>
For	O
example	O
,	O
many	O
graphics	B-Device
cards	I-Device
on	O
the	O
market	O
as	O
of	O
2010	O
are	O
dual	O
slot	O
graphics	B-Device
cards	I-Device
,	O
using	O
the	O
second	O
slot	O
as	O
a	O
place	O
to	O
put	O
an	O
active	O
heat	O
sink	O
with	O
a	O
fan	O
.	O
</s>
<s>
Some	O
cards	O
are	O
"	O
low-profile	O
"	O
cards	O
,	O
meaning	O
that	O
they	O
are	O
shorter	O
than	O
standard	O
cards	O
and	O
will	O
fit	O
in	O
a	O
lower	O
height	O
computer	B-General_Concept
chassis	I-General_Concept
.	O
</s>
<s>
(	O
There	O
is	O
a	O
"	O
low	O
profile	O
PCI	B-Protocol
card	I-Protocol
"	O
standard	O
that	O
specifies	O
a	O
much	O
smaller	O
bracket	O
and	O
board	O
area	O
)	O
.	O
</s>
<s>
The	O
group	O
of	O
expansion	B-Device
cards	I-Device
that	O
are	O
used	O
for	O
external	O
connectivity	O
,	O
such	O
as	O
network	B-Protocol
,	O
SAN	O
or	O
modem	B-Application
cards	O
,	O
are	O
commonly	O
referred	O
to	O
as	O
input/output	B-General_Concept
cards	O
(	O
or	O
I/O	B-Device
cards	I-Device
)	O
.	O
</s>
<s>
A	O
daughterboard	O
,	O
daughtercard	B-Device
,	O
mezzanine	B-Device
board	I-Device
or	O
piggyback	O
board	O
is	O
an	O
expansion	B-Device
card	I-Device
that	O
attaches	O
to	O
a	O
system	O
directly	O
.	O
</s>
<s>
Daughterboards	O
often	O
have	O
plugs	B-Protocol
,	O
sockets	O
,	O
pins	O
or	O
other	O
attachments	O
for	O
other	O
boards	O
.	O
</s>
<s>
Daughterboards	O
often	O
have	O
only	O
internal	O
connections	O
within	O
a	O
computer	O
or	O
other	O
electronic	O
devices	O
,	O
and	O
usually	O
access	O
the	O
motherboard	B-Device
directly	O
rather	O
than	O
through	O
a	O
computer	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
Daughterboards	O
are	O
sometimes	O
used	O
in	O
computers	O
in	O
order	O
to	O
allow	O
for	O
expansion	B-Device
cards	I-Device
to	O
fit	O
parallel	O
to	O
the	O
motherboard	B-Device
,	O
usually	O
to	O
maintain	O
a	O
small	O
form	O
factor	O
.	O
</s>
<s>
This	O
form	O
are	O
also	O
called	O
riser	B-Architecture
cards	I-Architecture
,	O
or	O
risers	O
.	O
</s>
<s>
Rather	O
than	O
redesigning	O
the	O
first	O
model	O
completely	O
,	O
a	O
daughterboard	O
may	O
be	O
added	O
to	O
a	O
special	O
connector	O
on	O
the	O
main	B-Device
board	I-Device
.	O
</s>
<s>
These	O
usually	O
fit	O
on	O
top	O
of	O
and	O
parallel	O
to	O
the	O
board	O
,	O
separated	O
by	O
spacers	O
or	O
standoffs	O
,	O
and	O
are	O
sometimes	O
called	O
mezzanine	B-Device
cards	I-Device
due	O
to	O
being	O
stacked	O
like	O
the	O
mezzanine	O
of	O
a	O
theatre	O
.	O
</s>
<s>
Wavetable	O
cards	O
(	O
sample-based	O
synthesis	O
cards	O
)	O
are	O
often	O
mounted	O
on	O
sound	B-Device
cards	I-Device
in	O
this	O
manner	O
.	O
</s>
<s>
the	O
400	O
pin	O
FPGA	O
Mezzanine	B-Device
Card	I-Device
(	O
FMC	O
)	O
;	O
</s>
<s>
the	O
172	O
pin	O
High	O
Speed	O
Mezzanine	B-Device
Card	I-Device
(	O
HSMC	O
)	O
;	O
</s>
<s>
the	O
PCI	B-Protocol
Mezzanine	B-Device
Card	I-Device
(	O
PMC	O
)	O
;	O
</s>
<s>
the	O
Advanced	B-Architecture
Mezzanine	I-Architecture
Card	I-Architecture
;	O
</s>
<s>
Examples	O
of	O
daughterboard-style	O
expansion	B-Device
cards	I-Device
include	O
:	O
</s>
<s>
Network	B-Protocol
Daughterboard	O
(	O
NDB	O
)	O
.	O
</s>
<s>
Commonly	O
integrates	O
:	O
bus	B-General_Concept
interfaces	O
logic	O
,	O
LLC	O
,	O
PHY	O
and	O
Magnetics	O
onto	O
a	O
single	O
board	O
.	O
</s>
