<s>
A	O
backplane	B-Architecture
(	O
or	O
"	O
backplane	B-Architecture
system	I-Architecture
"	O
)	O
is	O
a	O
group	O
of	O
electrical	B-Protocol
connectors	I-Protocol
in	O
parallel	O
with	O
each	O
other	O
,	O
so	O
that	O
each	O
pin	O
of	O
each	O
connector	O
is	O
linked	O
to	O
the	O
same	O
relative	O
pin	O
of	O
all	O
the	O
other	O
connectors	O
,	O
forming	O
a	O
computer	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
Backplanes	B-Architecture
commonly	O
use	O
a	O
printed	O
circuit	O
board	O
,	O
but	O
wire-wrapped	O
backplanes	B-Architecture
have	O
also	O
been	O
used	O
in	O
minicomputers	B-Architecture
and	O
high-reliability	O
applications	O
.	O
</s>
<s>
A	O
backplane	B-Architecture
is	O
generally	O
differentiated	O
from	O
a	O
motherboard	B-Device
by	O
the	O
lack	O
of	O
on-board	O
processing	O
and	O
storage	O
elements	O
.	O
</s>
<s>
A	O
backplane	B-Architecture
uses	O
plug-in	O
cards	O
for	O
storage	O
and	O
processing	O
.	O
</s>
<s>
Early	O
microcomputer	O
systems	O
like	O
the	O
Altair	B-Architecture
8800	I-Architecture
used	O
a	O
backplane	B-Architecture
for	O
the	O
processor	O
and	O
expansion	B-Device
cards	I-Device
.	O
</s>
<s>
Backplanes	B-Architecture
are	O
normally	O
used	O
in	O
preference	O
to	O
cables	O
because	O
of	O
their	O
greater	O
reliability	O
.	O
</s>
<s>
A	O
backplane	B-Architecture
does	O
not	O
suffer	O
from	O
this	O
problem	O
,	O
so	O
its	O
service	O
life	O
is	O
limited	O
only	O
by	O
the	O
longevity	O
of	O
its	O
connectors	O
.	O
</s>
<s>
For	O
example	O
,	O
DIN	O
41612	O
connectors	O
(	O
used	O
in	O
the	O
VMEbus	B-Architecture
system	O
)	O
have	O
three	O
durability	O
grades	O
built	O
to	O
withstand	O
(	O
respectively	O
)	O
50	O
,	O
400	O
and	O
500	O
insertions	O
and	O
removals	O
,	O
or	O
"	O
mating	O
cycles	O
"	O
.	O
</s>
<s>
To	O
transmit	O
information	O
,	O
Serial	O
Back-Plane	O
technology	O
uses	O
a	O
low-voltage	B-Architecture
differential	I-Architecture
signaling	I-Architecture
transmission	O
method	O
for	O
sending	O
information	O
.	O
</s>
<s>
In	O
addition	O
,	O
there	O
are	O
bus	O
expansion	O
cables	O
which	O
will	O
extend	O
a	O
computer	B-General_Concept
bus	I-General_Concept
to	O
an	O
external	O
backplane	B-Architecture
,	O
usually	O
located	O
in	O
an	O
enclosure	O
,	O
to	O
provide	O
more	O
or	O
different	O
slots	O
than	O
the	O
host	O
computer	O
provides	O
.	O
</s>
<s>
These	O
cable	O
sets	O
have	O
a	O
transmitter	O
board	O
located	O
in	O
the	O
computer	O
,	O
an	O
expansion	B-Device
board	I-Device
in	O
the	O
remote	O
backplane	B-Architecture
,	O
and	O
a	O
cable	O
between	O
the	O
two	O
.	O
</s>
<s>
Backplanes	B-Architecture
have	O
grown	O
in	O
complexity	O
from	O
the	O
simple	O
Industry	B-Architecture
Standard	I-Architecture
Architecture	I-Architecture
(	O
ISA	O
)	O
(	O
used	O
in	O
the	O
original	O
IBM	B-Device
PC	I-Device
)	O
or	O
S-100	B-Architecture
style	O
where	O
all	O
the	O
connectors	O
were	O
connected	O
to	O
a	O
common	O
bus	O
.	O
</s>
<s>
Due	O
to	O
limitations	O
inherent	O
in	O
the	O
Peripheral	B-Protocol
Component	I-Protocol
Interconnect	I-Protocol
(	O
PCI	B-Protocol
)	O
specification	O
for	O
driving	O
slots	O
,	O
backplanes	B-Architecture
are	O
now	O
offered	O
as	O
passive	O
and	O
active	O
.	O
</s>
<s>
True	O
passive	B-Architecture
backplanes	I-Architecture
offer	O
no	O
active	O
bus	O
driving	O
circuitry	O
.	O
</s>
<s>
Any	O
desired	O
arbitration	O
logic	O
is	O
placed	O
on	O
the	O
daughter	B-Device
cards	I-Device
.	O
</s>
<s>
Active	O
backplanes	B-Architecture
include	O
chips	O
which	O
buffer	B-General_Concept
the	O
various	O
signals	O
to	O
the	O
slots	O
.	O
</s>
<s>
The	O
distinction	O
between	O
the	O
two	O
is	O
n't	O
always	O
clear	O
,	O
but	O
may	O
become	O
an	O
important	O
issue	O
if	O
a	O
whole	O
system	O
is	O
expected	O
to	O
not	O
have	O
a	O
single	B-Architecture
point	I-Architecture
of	I-Architecture
failure	I-Architecture
(	O
SPOF	B-Architecture
)	O
.	O
</s>
<s>
Common	O
myth	O
around	O
passive	B-Architecture
backplane	I-Architecture
,	O
even	O
if	O
it	O
is	O
single	O
,	O
is	O
not	O
usually	O
considered	O
a	O
SPOF	B-Architecture
.	O
</s>
<s>
Therefore	O
,	O
we	O
are	O
seeing	O
newer	O
architectures	O
where	O
systems	O
use	O
high	O
speed	O
redundant	O
connectivity	O
to	O
interconnect	B-General_Concept
system	B-Device
boards	I-Device
point	O
to	O
point	O
with	O
No	B-Architecture
Single	I-Architecture
Point	I-Architecture
of	I-Architecture
Failure	I-Architecture
anywhere	O
in	O
the	O
system	O
.	O
</s>
<s>
When	O
a	O
backplane	B-Architecture
is	O
used	O
with	O
a	O
plug-in	O
single-board	B-Device
computer	I-Device
(	O
SBC	O
)	O
or	O
system	B-Device
host	I-Device
board	I-Device
(	O
SHB	O
)	O
,	O
the	O
combination	O
provides	O
the	O
same	O
functionality	O
as	O
a	O
motherboard	B-Device
,	O
providing	O
processing	O
power	O
,	O
memory	O
,	O
I/O	O
and	O
slots	O
for	O
plug-in	O
cards	O
.	O
</s>
<s>
While	O
there	O
are	O
a	O
few	O
motherboards	B-Device
that	O
offer	O
more	O
than	O
8	O
slots	O
,	O
that	O
is	O
the	O
traditional	O
limit	O
.	O
</s>
<s>
In	O
addition	O
,	O
as	O
technology	O
progresses	O
,	O
the	O
availability	O
and	O
number	O
of	O
a	O
particular	O
slot	O
type	O
may	O
be	O
limited	O
in	O
terms	O
of	O
what	O
is	O
currently	O
offered	O
by	O
motherboard	B-Device
manufacturers	O
.	O
</s>
<s>
However	O
,	O
backplane	B-Architecture
architecture	O
is	O
somewhat	O
unrelated	O
to	O
the	O
SBC	O
technology	O
plugged	O
into	O
it	O
.	O
</s>
<s>
Thus	O
,	O
a	O
PICMG	O
backplane	B-Architecture
can	O
provide	O
any	O
number	O
and	O
any	O
mix	O
of	O
ISA	O
,	O
PCI	B-Protocol
,	O
PCI-X	O
,	O
and	O
PCI-e	O
slots	O
,	O
limited	O
only	O
by	O
the	O
ability	O
of	O
the	O
SBC	O
to	O
interface	O
to	O
and	O
drive	O
those	O
slots	O
.	O
</s>
<s>
For	O
example	O
,	O
an	O
SBC	O
with	O
the	O
latest	O
i7	O
processor	O
could	O
interface	O
with	O
a	O
backplane	B-Architecture
providing	O
up	O
to	O
19	O
ISA	B-Architecture
slots	I-Architecture
to	O
drive	O
legacy	O
I/O	B-Device
cards	I-Device
.	O
</s>
<s>
Some	O
backplanes	B-Architecture
are	O
constructed	O
with	O
slots	O
for	O
connecting	O
to	O
devices	O
on	O
both	O
sides	O
,	O
and	O
are	O
referred	O
to	O
as	O
midplanes	O
.	O
</s>
<s>
Midplanes	O
are	O
often	O
used	O
in	O
computers	O
,	O
mostly	O
in	O
blade	B-Architecture
servers	I-Architecture
,	O
where	O
server	B-Architecture
blades	I-Architecture
reside	O
on	O
one	O
side	O
and	O
the	O
peripheral	O
(	O
power	O
,	O
networking	O
,	O
and	O
other	O
I/O	O
)	O
and	O
service	O
modules	O
reside	O
on	O
the	O
other	O
.	O
</s>
<s>
Some	O
people	O
use	O
the	O
term	O
"	O
midplane	O
"	O
to	O
describe	O
a	O
board	O
that	O
sits	O
between	O
and	O
connects	O
a	O
hard	O
drive	O
hot-swap	O
backplane	B-Architecture
and	O
redundant	O
power	O
supplies	O
.	O
</s>
<s>
Servers	O
commonly	O
have	O
a	O
backplane	B-Architecture
to	O
attach	O
hot	O
swappable	O
hard	O
drives	O
;	O
backplane	B-Architecture
pins	O
pass	O
directly	O
into	O
hard	O
drive	O
sockets	O
without	O
cables	O
.	O
</s>
<s>
They	O
may	O
have	O
single	O
connector	O
to	O
connect	O
one	O
disk	B-Device
array	I-Device
controller	I-Device
or	O
multiple	O
connectors	O
that	O
can	O
be	O
connected	O
to	O
one	O
or	O
more	O
controllers	O
in	O
arbitrary	O
way	O
.	O
</s>
<s>
Backplanes	B-Architecture
are	O
commonly	O
found	O
in	O
disk	B-Device
enclosures	I-Device
,	O
disk	B-General_Concept
arrays	I-General_Concept
,	O
and	O
servers	O
.	O
</s>
<s>
Backplanes	B-Architecture
for	O
SAS	O
and	O
SATA	O
HDDs	O
most	O
commonly	O
use	O
the	O
SGPIO	O
protocol	O
as	O
means	O
of	O
communication	O
between	O
the	O
host	B-Architecture
adapter	I-Architecture
and	O
the	O
backplane	B-Architecture
.	O
</s>
<s>
Alternatively	O
SCSI	B-Application
Enclosure	I-Application
Services	I-Application
can	O
be	O
used	O
.	O
</s>
<s>
With	O
Parallel	O
SCSI	O
subsystems	O
,	O
SAF-TE	B-Application
is	O
used	O
.	O
</s>
<s>
A	O
single-board	B-Device
computer	I-Device
meeting	O
the	O
PICMG	O
1.3	O
specification	O
and	O
compatible	O
with	O
a	O
PICMG	O
1.3	O
backplane	B-Architecture
is	O
referred	O
to	O
as	O
a	O
System	B-Device
Host	I-Device
Board	I-Device
.	O
</s>
<s>
In	O
the	O
Intel	O
Single-Board	B-Device
Computer	I-Device
world	O
,	O
PICMG	O
provides	O
standards	O
for	O
the	O
backplane	B-Architecture
interface	O
:	O
</s>
<s>
PICMG	O
1.0	O
,	O
1.1	O
and	O
1.2	O
provide	O
ISA	O
and	O
PCI	B-Protocol
support	O
,	O
with	O
1.2	O
adding	O
PCIX	O
support	O
.	O
</s>
<s>
PICMG	O
1.3	O
provides	O
PCI-Express	O
support	O
.	O
</s>
