<s>
The	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
XT	I-Device
(	O
model	O
5160	O
,	O
often	O
shortened	O
to	O
PC/XT	B-Device
)	O
is	O
the	O
second	O
computer	O
in	O
the	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
line	O
,	O
released	O
on	O
March	O
8	O
,	O
1983	O
.	O
</s>
<s>
Except	O
for	O
the	O
addition	O
of	O
a	O
built-in	O
hard	B-Device
drive	I-Device
and	O
extra	O
expansion	O
slots	O
,	O
it	O
is	O
very	O
similar	O
to	O
the	O
original	O
IBM	B-Device
PC	I-Device
model	O
5150	O
from	O
1981	O
.	O
</s>
<s>
Compared	O
to	O
the	O
original	O
IBM	B-Device
PC	I-Device
,	O
the	O
XT	O
has	O
the	O
following	O
major	O
differences	O
:	O
</s>
<s>
The	O
number	O
of	O
expansion	O
slots	O
in	O
the	O
original	O
IBM	B-Device
PC	I-Device
was	O
a	O
limiting	O
factor	O
for	O
the	O
product	O
,	O
since	O
essential	O
components	O
(	O
such	O
as	O
the	O
video	O
controller	O
,	O
disk	O
controller	O
and	O
printer	O
interface	O
)	O
each	O
came	O
as	O
separate	O
expansion	O
cards	O
and	O
could	O
quickly	O
fill	O
up	O
all	O
five	O
available	O
slots	O
,	O
requiring	O
the	O
user	O
to	O
swap	O
cards	O
in	O
and	O
out	O
as	O
tasks	O
demanded	O
.	O
</s>
<s>
While	O
the	O
slots	O
themselves	O
are	O
identical	O
to	O
those	O
in	O
the	O
original	O
PC	O
,	O
the	O
amount	O
of	O
physical	O
space	O
in	O
the	O
chassis	O
differs	O
,	O
so	O
two	O
of	O
the	O
new	O
slots	O
(	O
located	O
behind	O
the	O
hard	B-Device
drive	I-Device
)	O
cannot	O
accept	O
full-length	O
cards	O
.	O
</s>
<s>
The	O
5161	O
shipped	O
with	O
a	O
10MB	O
hard	B-Device
drive	I-Device
,	O
and	O
had	O
room	O
for	O
a	O
second	O
one	O
.	O
</s>
<s>
The	O
Expansion	O
Unit	O
can	O
also	O
contain	O
extra	O
memory	O
,	O
but	O
the	O
Extender	O
card	O
inserts	O
wait	B-Device
states	I-Device
for	O
memory	O
in	O
the	O
Expansion	O
Unit	O
,	O
so	O
it	O
may	O
be	O
preferable	O
to	O
install	O
memory	O
into	O
the	O
main	O
system	O
unit	O
.	O
</s>
<s>
The	O
5161	O
can	O
be	O
connected	O
to	O
either	O
an	O
XT	O
or	O
to	O
the	O
earlier	O
5150	O
(	O
the	O
original	O
IBM	B-Device
PC	I-Device
)	O
.	O
</s>
<s>
PC	B-Operating_System
DOS	I-Operating_System
2.0	O
offers	O
a	O
9-sector	O
floppy	O
disk	O
format	O
,	O
providing	O
180K/360K	O
(	O
single	O
-	O
vs.	O
dual-sided	O
)	O
capacity	O
per	O
disk	O
,	O
compared	O
to	O
the	O
160K/320K	O
provided	O
by	O
the	O
8-sector	O
format	O
of	O
previous	O
releases	O
.	O
</s>
<s>
Like	O
the	O
original	O
PC	O
,	O
the	O
XT	O
comes	O
with	O
IBM	B-Language
BASIC	I-Language
in	O
ROM	B-Device
.	O
</s>
<s>
The	O
XT	O
BIOS	O
also	O
displays	O
a	O
memory	O
count	O
during	O
the	O
POST	B-Device
,	O
unlike	O
the	O
original	O
PC	O
.	O
</s>
<s>
The	O
XT	O
has	O
a	O
desktop	O
case	O
similar	O
to	O
that	O
of	O
the	O
IBM	B-Device
PC	I-Device
.	O
</s>
<s>
The	O
3270	B-Device
PC	I-Device
,	O
a	O
variant	O
of	O
the	O
XT	O
featuring	O
3270	B-Operating_System
terminal	I-Operating_System
emulation	O
,	O
was	O
released	O
in	O
October	O
1983	O
.	O
</s>
<s>
Submodel	O
068	O
and	O
078	O
,	O
released	O
in	O
1985	O
,	O
offered	O
dual-floppy	O
configurations	O
without	O
a	O
hard	B-Device
drive	I-Device
as	O
well	O
,	O
and	O
the	O
new	O
Enhanced	B-Device
Graphics	I-Device
Adapter	I-Device
and	O
Professional	B-Device
Graphics	I-Device
Adapter	I-Device
became	O
available	O
as	O
video	O
card	O
options	O
.	O
</s>
<s>
Submodels	O
267	O
,	O
277	O
and	O
088	O
had	O
the	O
original	O
keyboard	O
,	O
but	O
3.5	O
"	O
floppy	O
drives	O
became	O
available	O
and	O
20MB	O
Seagate	O
ST-225	O
hard	B-Device
disks	I-Device
in	O
5.25	O
"	O
half-height	O
size	O
replaced	O
the	O
full-height	O
10MB	O
drives	O
.	O
</s>
<s>
Submodel	O
788	O
was	O
the	O
only	O
XT	O
sold	O
with	O
the	O
Color	B-Device
Graphics	I-Device
Adapter	I-Device
as	O
a	O
standard	O
feature	O
.	O
</s>
<s>
Submodels	O
568	O
,	O
588	O
,	O
and	O
589	O
were	O
used	O
as	O
basis	O
for	O
the	O
XT/370	O
;	O
they	O
had	O
an	O
additional	O
(	O
co	O
-	O
)	O
processor	O
board	O
that	O
could	O
execute	O
System/370	B-Device
instructions	O
.	O
</s>
<s>
An	O
XT-based	O
machine	O
with	O
a	O
Series/1	B-Device
co-processor	O
board	O
existed	O
as	O
well	O
,	O
but	O
it	O
had	O
its	O
own	O
System	O
Unit	O
number	O
,	O
the	O
IBM	O
4950	O
.	O
</s>
<s>
In	O
1986	O
the	O
XT	O
286	B-General_Concept
(	O
model	O
5162	O
)	O
was	O
released	O
with	O
a	O
6MHz	O
Intel	B-General_Concept
80286	I-General_Concept
processor	O
.	O
</s>
<s>
Despite	O
being	O
marketed	O
as	O
a	O
lower-tier	O
model	O
than	O
the	O
IBM	B-Operating_System
AT	I-Operating_System
,	O
this	O
system	O
runs	O
many	O
applications	O
faster	O
than	O
the	O
ATs	O
of	O
the	O
time	O
with	O
6MHz	O
286	B-General_Concept
processors	O
,	O
since	O
it	O
has	O
zero-wait	O
state	O
RAM	O
.	O
</s>
<s>
It	O
shipped	O
with	O
640KB	O
RAM	O
standard	O
,	O
an	O
AT-style	O
1.2MB	O
high-density	O
diskette	O
drive	O
and	O
a	O
20MB	O
hard	B-Device
disk	I-Device
.	O
</s>
<s>
The	O
XT	O
286	B-General_Concept
uses	O
a	O
157-watt	O
power	O
supply	O
,	O
which	O
can	O
internally	O
switch	O
between	O
115	O
or	O
230V	O
AC	O
operation	O
.	O
</s>
<s>
The	O
XT	O
was	O
well	O
received	O
,	O
although	O
PC	B-Operating_System
DOS	I-Operating_System
2.0	O
was	O
regarded	O
as	O
a	O
greater	O
improvement	O
than	O
any	O
of	O
the	O
hardware	O
changes	O
,	O
and	O
by	O
the	O
end	O
of	O
1983	O
IBM	O
was	O
selling	O
every	O
unit	O
they	O
made	O
.	O
</s>
<s>
The	O
Compaq	B-Device
Portable	I-Device
also	O
came	O
out	O
in	O
March	O
1983	O
,	O
and	O
would	O
prove	O
a	O
popular	O
competitor	O
.	O
</s>
<s>
Sometimes	O
called	O
the	O
"	O
first	O
PC	O
clone	O
"	O
and	O
first	O
"	O
legal	O
clone	O
"	O
,	O
that	O
distinction	O
may	O
go	O
to	O
another	O
offering	O
:	O
Columbia	B-Device
Data	I-Device
Products	I-Device
 '	O
MPC	O
1600	O
"	O
Multi	O
Personal	B-Device
Computer	I-Device
"	O
,	O
in	O
June	O
1982	O
.	O
</s>
<s>
Other	O
"	O
clones	O
"	O
included	O
the	O
Seequa	B-Device
Chameleon	I-Device
,	O
the	O
Hyperion	B-Device
,	O
Eagle	O
Computer	O
's	O
Eagle	O
1600	O
that	O
September	O
and	O
the	O
Corona	O
PC	O
.	O
</s>
<s>
AT&T	O
,	O
who	O
owned	O
a	O
25%	O
share	O
of	O
Olivetti	O
,	O
released	O
the	O
AT&T	B-Operating_System
PC	I-Operating_System
6300	I-Operating_System
in	O
June	O
1984	O
,	O
which	O
was	O
a	O
re-branded	O
version	O
of	O
the	O
Olivetti	B-Operating_System
M24	I-Operating_System
.	O
</s>
<s>
The	O
PC	O
6300	O
offered	O
the	O
16-bit	O
8086	O
clocked	O
at	O
a	O
faster	O
8	O
MHz	O
speed	O
that	O
was	O
technically	O
superior	O
to	O
IBM	O
's	O
PC	B-Device
XT	I-Device
.	O
</s>
