<s>
In	O
the	O
era	O
of	O
IBM	O
compatible	O
personal	B-Device
computers	I-Device
,	O
the	O
AT	B-Device
form	I-Device
factor	I-Device
comprises	O
the	O
dimensions	O
and	O
layout	O
(	O
form	O
factor	O
)	O
of	O
the	O
motherboard	B-Device
for	O
the	O
IBM	B-Operating_System
AT	I-Operating_System
.	O
</s>
<s>
Baby	O
AT	O
motherboards	B-Device
are	O
a	O
little	O
smaller	O
,	O
measuring	O
8.5	O
"	O
by	O
13	O
"	O
.	O
</s>
<s>
Like	O
the	O
IBM	B-Device
PC	I-Device
and	O
IBM	B-Device
XT	I-Device
models	O
before	O
it	O
,	O
many	O
third-party	O
manufacturers	O
produced	O
motherboards	B-Device
compatible	O
with	O
the	O
IBM	B-Operating_System
AT	I-Operating_System
form	O
factor	O
,	O
allowing	O
end	O
users	O
to	O
upgrade	O
their	O
computers	O
for	O
faster	O
processors	O
.	O
</s>
<s>
The	O
IBM	B-Operating_System
AT	I-Operating_System
became	O
a	O
widely	O
copied	O
design	O
in	O
the	O
booming	O
home	O
computer	O
market	O
of	O
the	O
1980s	O
.	O
</s>
<s>
Since	O
1997	O
,	O
the	O
AT	B-Device
form	I-Device
factor	I-Device
has	O
been	O
largely	O
supplanted	O
by	O
ATX	B-Language
.	O
</s>
<s>
The	O
original	O
AT	O
motherboard	B-Device
,	O
later	O
known	O
as	O
"	O
Full	O
AT	O
"	O
,	O
is	O
,	O
which	O
means	O
it	O
will	O
not	O
fit	O
in	O
"	O
mini	O
desktop	O
"	O
or	O
"	O
minitower	O
cases	O
"	O
.	O
</s>
<s>
The	O
board	O
's	O
size	O
also	O
means	O
that	O
it	O
takes	O
up	O
space	O
behind	O
the	O
drive	B-Device
bays	I-Device
,	O
making	O
installation	O
of	O
new	O
drives	O
more	O
difficult	O
.	O
</s>
<s>
(	O
In	O
IBM	O
's	O
original	O
heavy-gauge	O
steel	O
case	O
,	O
the	O
two	O
"	O
full-height	B-Device
drive	I-Device
bays	O
overhang	O
the	O
front	O
of	O
the	O
motherboard	B-Device
.	O
</s>
<s>
More	O
precisely	O
,	O
the	O
left	O
bay	O
overhangs	O
the	O
motherboard	B-Device
,	O
while	O
the	O
right	O
bay	O
is	O
subdivided	O
into	O
two	O
half-height	B-Device
bays	O
and	O
additionally	O
extends	O
downward	O
toward	O
the	O
bottom	O
of	O
the	O
chassis	O
,	O
allowing	O
a	O
second	O
full-height	B-Device
fixed	O
disk	O
to	O
be	O
installed	O
below	O
a	O
single	O
half-height	B-Device
drive	O
.	O
)	O
</s>
<s>
The	O
power	O
connectors	O
for	O
AT	O
motherboards	B-Device
are	O
two	O
nearly	O
identical	O
6-pin	O
plugs	O
and	O
sockets	O
.	O
</s>
<s>
In	O
1987	O
,	O
the	O
Baby	O
AT	B-Device
form	I-Device
factor	I-Device
was	O
introduced	O
,	O
based	O
on	O
the	O
motherboard	B-Device
found	O
in	O
the	O
IBM	B-Device
PC/XT	I-Device
286	B-General_Concept
(	O
5162	O
)	O
and	O
soon	O
after	O
all	O
computer	O
makers	O
abandoned	O
AT	O
for	O
the	O
cheaper	O
and	O
smaller	O
Baby	O
AT	B-Device
form	I-Device
factor	I-Device
,	O
using	O
it	O
for	O
computers	O
that	O
spanned	O
several	O
generations	O
,	O
from	O
those	O
that	O
used	O
286	B-General_Concept
processors	O
to	O
the	O
P5	B-General_Concept
Pentium	B-General_Concept
and	O
a	O
limited	O
number	O
of	O
Pentium	B-General_Concept
II	I-General_Concept
systems	O
.	O
</s>
<s>
These	O
motherboards	B-Device
have	O
similar	O
mounting	O
hole	O
positions	O
and	O
the	O
same	O
eight	O
card	O
slot	O
locations	O
as	O
those	O
with	O
the	O
AT	B-Device
form	I-Device
factor	I-Device
,	O
but	O
are	O
wide	O
and	O
marginally	O
shorter	O
than	O
full-size	O
AT	O
boards	O
,	O
with	O
a	O
maximum	O
length	O
of	O
.	O
</s>
<s>
The	O
size	O
and	O
flexibility	O
of	O
this	O
kind	O
of	O
motherboard	B-Device
were	O
the	O
key	O
to	O
success	O
of	O
this	O
format	O
.	O
</s>
<s>
The	O
development	O
of	O
bigger	O
CPU	O
coolers	O
—	O
and	O
the	O
fact	O
that	O
they	O
blocked	O
full-length	O
PCI	O
and	O
ISA	O
cards	O
—	O
spelled	O
the	O
end	O
of	O
Baby	O
AT	O
and	O
was	O
the	O
main	O
impetus	O
for	O
its	O
successor	O
ATX	B-Language
.	O
</s>
<s>
In	O
1995	O
,	O
Intel	O
introduced	O
ATX	B-Language
,	O
a	O
form	O
factor	O
which	O
gradually	O
replaced	O
older	O
Baby	O
AT	O
motherboards	B-Device
.	O
</s>
<s>
During	O
the	O
late	O
1990s	O
,	O
a	O
great	O
majority	O
of	O
boards	O
were	O
either	O
Baby	O
AT	O
or	O
ATX	B-Language
.	O
</s>
<s>
Many	O
motherboard	B-Device
manufacturers	O
favored	O
Baby	O
AT	O
over	O
ATX	B-Language
as	O
many	O
computer	O
cases	O
and	O
power	O
supplies	O
in	O
the	O
industry	O
were	O
still	O
designed	O
for	O
AT	O
boards	O
and	O
not	O
ATX	B-Language
boards	O
.	O
</s>
<s>
Also	O
,	O
the	O
lack	O
of	O
an	O
eighth	O
slot	O
on	O
ATX	B-Language
motherboards	B-Device
kept	O
it	O
from	O
being	O
used	O
in	O
some	O
servers	O
.	O
</s>
<s>
Later	O
Baby	O
AT	O
boards	O
supported	O
both	O
AT	O
and	O
ATX	B-Language
power	O
connectors	O
in	O
addition	O
to	O
ATX	B-Language
features	O
such	O
as	O
standby	O
power	O
(	O
allowing	O
for	O
a	O
low	O
voltage	O
power	O
switch	O
,	O
as	O
well	O
as	O
Wake-on-LAN/Wake	O
-on-Modem	O
Ring	O
)	O
and	O
USB	B-Protocol
by	O
use	O
of	O
an	O
ATX	B-Language
Form	O
Card	O
.	O
</s>
<s>
After	O
the	O
industry	O
shifted	O
to	O
ATX	B-Language
motherboard	B-Device
configurations	O
,	O
it	O
became	O
common	O
to	O
design	O
cases	O
and	O
power	O
supplies	O
to	O
support	O
both	O
Baby	O
AT	O
and	O
ATX	B-Language
motherboards	B-Device
.	O
</s>
