<s>
The	O
IBM	O
PCjr	O
(	O
pronounced	O
"	O
PC	O
junior	O
"	O
)	O
was	O
a	O
home	O
computer	O
produced	O
and	O
marketed	O
by	O
IBM	O
from	O
March	O
1984	O
to	O
May	O
1985	O
,	O
intended	O
as	O
a	O
lower-cost	O
variant	O
of	O
the	O
IBM	B-Device
PC	I-Device
with	O
hardware	O
capabilities	O
better	O
suited	O
for	O
video	O
games	O
,	O
in	O
order	O
to	O
compete	O
more	O
directly	O
with	O
other	O
home	O
computers	O
such	O
as	O
the	O
Apple	B-Device
II	I-Device
and	O
Commodore	O
64	O
.	O
</s>
<s>
It	O
retained	O
the	O
IBM	B-Device
PC	I-Device
's	O
8088	B-Device
CPU	B-Device
and	O
BIOS	B-Operating_System
interface	O
,	O
but	O
provided	O
enhanced	O
graphics	O
and	O
sound	O
,	O
ROM	B-Protocol
cartridge	I-Protocol
slots	O
,	O
built-in	O
joystick	O
ports	O
,	O
and	O
an	O
infrared	O
wireless	O
keyboard	O
.	O
</s>
<s>
It	O
was	O
only	O
partially	O
IBM	O
compatible	O
,	O
limiting	O
support	O
for	O
IBM	O
's	O
software	O
library	O
,	O
its	O
chiclet	B-Device
keyboard	I-Device
was	O
widely	O
criticized	O
for	O
its	O
poor	O
quality	O
,	O
expandability	O
was	O
limited	O
,	O
and	O
it	O
was	O
initially	O
offered	O
with	O
a	O
maximum	O
of	O
of	O
RAM	O
,	O
insufficient	O
for	O
many	O
PC	O
programs	O
.	O
</s>
<s>
A	O
related	O
machine	O
,	O
the	O
IBM	B-Device
JX	I-Device
,	O
was	O
sold	O
in	O
the	O
Japan	O
,	O
Australia	O
and	O
New	O
Zealand	O
markets	O
.	O
</s>
<s>
The	O
PCjr	O
chassis	O
is	O
made	O
entirely	O
of	O
plastic	O
,	O
unlike	O
the	O
all-steel	O
chassis	O
of	O
the	O
IBM	B-Device
PC	I-Device
.	O
</s>
<s>
The	O
front	O
of	O
the	O
PCjr	O
exposes	O
a	O
pair	O
of	O
cartridge	B-Protocol
slots	O
in	O
which	O
the	O
user	O
can	O
insert	O
software	O
on	O
ROM	B-Protocol
cartridges	I-Protocol
,	O
as	O
was	O
common	O
with	O
other	O
home	O
computers	O
.	O
</s>
<s>
When	O
a	O
ROM	B-Protocol
cartridge	I-Protocol
is	O
inserted	O
,	O
the	O
machine	O
automatically	O
restarts	O
and	O
boots	O
off	O
of	O
the	O
ROM	O
,	O
without	O
requiring	O
the	O
user	O
to	O
manually	O
reboot	O
.	O
</s>
<s>
Cartridges	B-Protocol
can	O
also	O
replace	O
the	O
system	B-Operating_System
BIOS	I-Operating_System
and	O
other	O
firmware	O
.	O
</s>
<s>
A	O
number	O
of	O
patches	O
from	O
various	O
vendors	O
are	O
included	O
on	O
a	O
single	O
"	O
combo-cartridge	O
"	O
,	O
licensed	O
and	O
sold	O
by	O
PC	O
Enterprises	O
,	O
to	O
support	O
add-on	O
hardware	O
,	O
bypass	O
certain	O
limitations	O
of	O
design	O
,	O
and	O
keep	O
up	O
with	O
changing	O
OS	O
requirements	O
.	O
</s>
<s>
Like	O
the	O
IBM	B-Device
PC	I-Device
,	O
the	O
PCjr	O
uses	O
an	O
Intel	B-Device
8088	I-Device
clocked	O
at	O
4.77MHz	O
.	O
</s>
<s>
Despite	O
using	O
the	O
same	O
CPU	B-Device
and	O
clockspeed	O
,	O
performance	O
is	O
often	O
inferior	O
to	O
the	O
PC	O
,	O
because	O
access	O
to	O
system	O
RAM	O
is	O
delayed	O
by	O
wait	B-Device
states	I-Device
added	O
by	O
the	O
Video	O
Gate	O
Array	O
to	O
synchronize	O
shared	O
access	O
to	O
RAM	O
between	O
the	O
CPU	B-Device
and	O
the	O
video	O
hardware	O
.	O
</s>
<s>
IBM	O
claimed	O
that	O
an	O
average	O
of	O
two	O
wait	B-Device
states	I-Device
are	O
added	O
,	O
but	O
the	O
designers	O
of	O
the	O
Tandy	O
1000	O
,	O
a	O
clone	O
of	O
the	O
PCjr	O
,	O
claimed	O
that	O
six	O
was	O
a	O
more	O
accurate	O
figure	O
.	O
</s>
<s>
This	O
delay	O
only	O
applies	O
to	O
software	O
resident	O
in	O
the	O
first	O
64	O
KB	O
or	O
128	O
KB	O
of	O
RAM	O
inside	O
the	O
system	O
unit	O
itself	O
,	O
and	O
not	O
to	O
programs	O
or	O
data	O
located	O
in	O
ROM	O
-	O
including	O
software	O
on	O
ROM	B-Protocol
cartridges	I-Protocol
plugged	O
into	O
the	O
front	O
of	O
the	O
PCjr	O
-	O
or	O
in	O
additional	O
RAM	O
in	O
a	O
sidecar	O
attachment	O
.	O
</s>
<s>
The	O
most	O
common	O
instances	O
in	O
which	O
this	O
maximum	O
speed	O
would	O
be	O
achieved	O
are	O
when	O
running	O
games	O
or	O
productivity	O
applications	O
from	O
ROM	B-Protocol
cartridges	I-Protocol
.	O
</s>
<s>
In	O
fact	O
,	O
because	O
the	O
PCjr	O
video	O
subsystem	O
continuously	O
refreshes	O
the	O
system	O
internal	O
DRAM	O
transparently	O
,	O
without	O
disturbing	O
the	O
CPU	B-Device
,	O
programs	O
running	O
from	O
ROM	O
on	O
the	O
PCjr	O
may	O
actually	O
run	O
slightly	O
faster	O
on	O
the	O
PCjr	O
than	O
on	O
an	O
IBM	B-Device
PC	I-Device
or	O
XT	O
.	O
</s>
<s>
Unlike	O
the	O
IBM	B-Device
PC	I-Device
,	O
which	O
required	O
a	O
separate	O
video	O
card	O
,	O
the	O
PCjr	O
display	O
hardware	O
was	O
built	O
in	O
to	O
the	O
system	O
board	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
the	O
only	O
cards	O
available	O
from	O
IBM	O
for	O
the	O
PC	O
were	O
the	O
monochrome	O
MDA	B-Device
and	O
color	O
CGA	B-Device
boards	O
.	O
</s>
<s>
PCjr	O
graphics	O
were	O
similar	O
to	O
CGA	B-Device
,	O
with	O
several	O
new	O
video	O
modes	O
:	O
</s>
<s>
The	O
primary	O
improvement	O
over	O
CGA	B-Device
is	O
the	O
greater	O
color	O
depth	O
.	O
</s>
<s>
CGA	B-Device
could	O
only	O
display	O
4	O
colors	O
in	O
its	O
medium-resolution	O
mode	O
,	O
and	O
2	O
colors	O
in	O
high-resolution	O
.	O
</s>
<s>
Multiple	O
text	O
or	O
graphics	O
pages	O
can	O
be	O
used	O
for	O
page-flipping	B-Algorithm
as	O
long	O
as	O
there	O
is	O
enough	O
memory	O
,	O
a	O
feature	O
missing	O
from	O
the	O
CGA	B-Device
.	O
</s>
<s>
The	O
CGA	B-Device
also	O
did	O
not	O
provide	O
a	O
VBLANK	O
interrupt	O
,	O
making	O
it	O
hard	O
to	O
detect	O
when	O
the	O
screen	O
was	O
beginning	O
to	O
be	O
drawn	O
,	O
but	O
the	O
PCjr	O
provides	O
this	O
on	O
IRQ	O
5	O
,	O
an	O
important	O
feature	O
for	O
smooth	O
page-flipping	B-Algorithm
.	O
</s>
<s>
The	O
video	O
system	O
also	O
has	O
a	O
"	O
blink	O
"	O
feature	O
which	O
toggles	O
the	O
palette	O
between	O
the	O
first	O
and	O
second	O
groups	O
of	O
eight	O
palette	O
registers	O
at	O
the	O
same	O
rate	O
used	O
for	O
the	O
PCs	B-Device
blinking	O
text	O
attribute	O
,	O
and	O
a	O
palette	O
bit-masking	O
feature	O
that	O
can	O
be	O
used	O
to	O
switch	O
between	O
palette	O
subsets	O
without	O
reprogramming	O
palette	O
registers	O
.	O
</s>
<s>
Unlike	O
CGA	B-Device
,	O
PCjr	O
has	O
palette	O
registers	O
which	O
allow	O
the	O
colors	O
in	O
all	O
modes	O
to	O
be	O
chosen	O
from	O
the	O
full	O
16-color	O
RGBI	O
palette	O
.	O
</s>
<s>
When	O
the	O
BIOS	B-Operating_System
is	O
used	O
to	O
set	O
a	O
video	O
mode	O
,	O
it	O
sets	O
up	O
the	O
palette	O
table	O
to	O
emulate	O
the	O
CGA	B-Device
color	O
palette	O
for	O
that	O
mode	O
.	O
</s>
<s>
The	O
monitor	O
included	O
with	O
the	O
PCjr	O
is	O
a	O
12	O
"	O
TTL	O
RGBI	O
display	O
like	O
those	O
supported	O
by	O
the	O
CGA	B-Device
,	O
but	O
including	O
an	O
internal	O
amplified	O
speaker	O
.	O
</s>
<s>
Also	O
like	O
CGA	B-Device
,	O
the	O
PCjr	O
supported	O
composite	O
video	O
out	O
for	O
use	O
with	O
a	O
TV	O
or	O
composite	O
monitor	O
.	O
</s>
<s>
A	O
Motorola	B-General_Concept
6845	I-General_Concept
CRTC	O
like	O
the	O
one	O
used	O
in	O
the	O
MDA	B-Device
and	O
CGA	B-Device
adapters	O
,	O
and	O
a	O
custom	O
IBM	O
chip	O
called	O
the	O
Video	O
Gate	O
Array	O
(	O
VGA	B-Protocol
)	O
comprise	O
the	O
PCjr	O
video	O
hardware	O
.	O
</s>
<s>
The	O
6845	B-General_Concept
is	O
responsible	O
for	O
the	O
basic	O
raster	O
timing	O
and	O
video	O
data	O
address	O
sequencing	O
,	O
and	O
the	O
Video	O
Gate	O
Array	O
contains	O
all	O
the	O
additional	O
timing	O
logic	O
,	O
video	O
data	O
demultiplexing	O
logic	O
,	O
color	O
processing	O
logic	O
,	O
and	O
programmable	O
palette	O
table	O
logic	O
,	O
as	O
well	O
as	O
the	O
logic	O
for	O
multiplexing	O
RAM	O
access	O
between	O
the	O
8088	B-Device
CPU	B-Device
and	O
the	O
video	O
generation	O
circuitry	O
.	O
</s>
<s>
The	O
6845	B-General_Concept
CRTC	I-General_Concept
and	O
the	O
VGA	B-Protocol
together	O
are	O
responsible	O
for	O
refreshing	O
the	O
internal	O
DRAM	O
of	O
the	O
PCjr	O
,	O
which	O
complicates	O
the	O
process	O
of	O
switching	O
video	O
modes	O
on	O
the	O
PCjr	O
.	O
</s>
<s>
Resetting	O
the	O
VGA	B-Protocol
,	O
which	O
must	O
be	O
done	O
during	O
certain	O
video	O
mode	O
switches	O
,	O
must	O
be	O
done	O
by	O
code	O
not	O
running	O
from	O
system	O
RAM	O
,	O
and	O
if	O
the	O
CRTC	O
or	O
the	O
VGA	B-Protocol
is	O
disabled	O
for	O
too	O
long	O
,	O
the	O
contents	O
of	O
the	O
internal	O
RAM	O
can	O
be	O
lost	O
.	O
</s>
<s>
Of	O
the	O
three	O
new	O
modes	O
,	O
160x200x16	O
mode	O
has	O
the	O
same	O
layout	O
as	O
CGA	B-Device
graphics	I-Device
modes	O
;	O
the	O
odd	O
and	O
even	O
scanlines	O
are	O
stored	O
in	O
the	O
first	O
and	O
second	O
half	O
of	O
the	O
video	O
buffer	O
,	O
each	O
half	O
being	O
8k	O
in	O
size	O
,	O
and	O
every	O
four	O
bits	O
represents	O
one	O
pixel	O
.	O
</s>
<s>
The	O
PCjr	O
's	O
sound	O
is	O
provided	O
by	O
a	O
Texas	B-Device
Instruments	I-Device
SN76496	I-Device
which	O
can	O
produce	O
three	O
square	O
waves	O
of	O
varying	O
amplitude	O
and	O
frequency	O
along	O
with	O
a	O
noise	O
channel	O
powered	O
by	O
a	O
shift	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
The	O
PCjr	O
design	O
also	O
allows	O
for	O
an	O
analog	O
sound	O
source	O
in	O
an	O
expansion-bus	O
"	O
sidecar	O
"	O
module	O
,	O
and	O
a	O
software-controlled	O
internal	O
analog	O
switch	O
can	O
select	O
the	O
source	O
for	O
the	O
sound	O
output	O
from	O
among	O
the	O
PC	B-Device
speaker	I-Device
,	O
the	O
SN76489	B-Device
,	O
the	O
cassette	O
port	O
,	O
or	O
the	O
expansion-bus	O
sound	O
source	O
.	O
</s>
<s>
This	O
is	O
a	O
chiclet	B-Device
keyboard	I-Device
with	O
small	O
,	O
flat	O
,	O
calculator	O
style	O
plastic	O
keycaps	O
.	O
</s>
<s>
The	O
PCjr	O
also	O
has	O
a	O
light	B-Device
pen	I-Device
port	O
.	O
</s>
<s>
Besides	O
being	O
used	O
for	O
a	O
light	B-Device
pen	I-Device
(	O
a	O
rarely	O
purchased	O
option	O
)	O
,	O
this	O
port	O
can	O
be	O
used	O
in	O
combination	O
with	O
the	O
serial	O
port	O
to	O
supply	O
voltage	O
to	O
a	O
Mouse	O
Systems	O
optical	O
mouse	O
of	O
the	O
same	O
design	O
as	O
those	O
for	O
Sun	O
workstations	O
.	O
</s>
<s>
The	O
primary	O
OS	O
for	O
the	O
PCjr	O
was	O
PC	B-Operating_System
DOS	I-Operating_System
,	O
like	O
the	O
IBM	B-Device
PC	I-Device
,	O
and	O
it	O
supported	O
a	O
large	O
amount	O
of	O
PC	O
software	O
,	O
with	O
some	O
incompatibilities	O
.	O
</s>
<s>
PC	B-Operating_System
DOS	I-Operating_System
2.10	O
is	O
the	O
minimum	O
version	O
of	O
DOS	O
required	O
for	O
the	O
PCjr	O
.	O
</s>
<s>
Like	O
the	O
original	O
PC	O
,	O
the	O
PCjr	O
has	O
BASIC	O
in	O
ROM	O
,	O
but	O
includes	O
Cartridge	B-Protocol
BASIC	O
instead	O
of	O
Cassette	O
BASIC	O
.	O
</s>
<s>
In	O
addition	O
to	O
cartridge	B-Protocol
support	O
,	O
it	O
extended	O
the	O
standard	O
IBM	O
BASIC	O
with	O
commands	O
to	O
support	O
the	O
new	O
video	O
and	O
audio	O
functionality	O
.	O
</s>
<s>
The	O
system	O
will	O
boot	O
into	O
Cartridge	B-Protocol
BASIC	O
if	O
no	O
cartridge	B-Protocol
or	O
boot	O
disk	O
is	O
present	O
.	O
</s>
<s>
The	O
register	O
mapping	O
of	O
the	O
PCjr	O
's	O
video	O
hardware	O
is	O
different	O
from	O
the	O
IBM	B-Device
CGA	I-Device
card	O
,	O
so	O
software	O
that	O
tries	O
to	O
modify	O
or	O
read	O
registers	O
directly	O
will	O
not	O
work	O
.	O
</s>
<s>
Alteration	O
of	O
other	O
CRTC	O
registers	O
cannot	O
be	O
assumed	O
to	O
produce	O
the	O
same	O
results	O
from	O
the	O
PCjr	O
video	O
system	O
as	O
from	O
the	O
CGA	B-Device
.	O
</s>
<s>
Programs	O
for	O
the	O
CGA	B-Device
that	O
manipulate	O
the	O
CRTC	O
start	O
address	O
,	O
and	O
that	O
rely	O
on	O
address	O
wrap-around	O
above	O
address	O
0xBC000	O
,	O
may	O
not	O
work	O
correctly	O
on	O
the	O
PCjr	O
because	O
it	O
always	O
has	O
a	O
32KB	O
contiguous	O
block	O
of	O
RAM	O
in	O
the	O
video	O
area	O
from	O
address	O
0xB8000	O
through	O
0xBFFFF	O
.	O
</s>
<s>
The	O
floppy	O
controller	O
on	O
the	O
PCjr	O
also	O
had	O
its	O
I/O	O
registers	O
mapped	O
into	O
different	O
ports	O
than	O
on	O
the	O
PC	O
,	O
and	O
since	O
the	O
PCjr	O
did	O
not	O
have	O
DMA	O
,	O
the	O
BIOS	B-Operating_System
routines	O
for	O
handling	O
floppy	O
access	O
were	O
different	O
and	O
more	O
complex	O
than	O
those	O
on	O
the	O
PC	O
.	O
</s>
<s>
The	O
rumors	O
described	O
Peanut	O
as	O
a	O
home	O
computer	O
with	O
of	O
memory	O
that	O
would	O
be	O
IBM	B-Device
PC	I-Device
compatible	O
,	O
benefit	O
from	O
IBM	O
's	O
service	O
network	O
and	O
,	O
at	O
to	O
,	O
be	O
less	O
expensive	O
than	O
the	O
Apple	B-Device
IIe	I-Device
.	O
</s>
<s>
Experts	O
predicted	O
,	O
according	O
to	O
The	O
Washington	O
Post	O
,	O
that	O
the	O
PCjr	O
would	O
"	O
quickly	O
become	O
the	O
standard	O
by	O
which	O
all	O
other	O
home	O
computers	O
are	O
measured	O
"	O
and	O
estimated	O
sales	O
of	O
one	O
million	O
or	O
more	O
in	O
1984	O
,	O
expecting	O
the	O
PCjr	O
to	O
change	O
the	O
home-computer	O
market	O
in	O
a	O
similar	O
way	O
to	O
how	O
the	O
IBM	B-Device
PC	I-Device
had	O
changed	O
the	O
business-microcomputer	O
market	O
.	O
</s>
<s>
Texas	O
Instruments	O
left	O
the	O
market	O
four	O
days	O
before	O
IBM	O
's	O
announcement	O
,	O
after	O
losing	O
in	O
nine	O
months	O
against	O
Commodore	O
by	O
selling	O
its	O
99/4A	B-Device
for	O
as	O
low	O
as	O
.	O
</s>
<s>
Prominent	O
among	O
launch	O
titles	O
was	O
Sierra	O
's	O
graphical	O
adventure	O
King	B-Device
's	I-Device
Quest	I-Device
I	I-Device
,	O
much	O
of	O
whose	O
budget	O
was	O
paid	O
by	O
IBM	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
significant	O
complaints	O
about	O
the	O
PCjr	O
was	O
its	O
chiclet	B-Device
keyboard	I-Device
,	O
which	O
was	O
described	O
as	O
unsuitable	O
for	O
serious	O
typing	O
and	O
"	O
nearly	O
useless.	O
"	O
</s>
<s>
The	O
PCjr	O
cost	O
more	O
than	O
twice	O
as	O
much	O
as	O
the	O
C64	O
and	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
,	O
while	O
inferior	O
to	O
both	O
for	O
videogames	O
.	O
</s>
<s>
Consumers	O
were	O
reportedly	O
much	O
more	O
excited	O
about	O
the	O
also-new	O
Macintosh	B-Device
128K	I-Device
,	O
which	O
was	O
more	O
sophisticated	O
but	O
only	O
cost	O
more	O
,	O
with	O
accessories	O
and	O
software	O
.	O
</s>
<s>
The	O
Macintosh	B-Device
reportedly	O
outsold	O
the	O
IBM	O
product	O
during	O
their	O
first	O
two	O
months	O
on	O
the	O
market	O
.	O
</s>
<s>
The	O
IIe	B-Device
was	O
the	O
PCjr	O
's	O
most	O
direct	O
competition	O
.	O
</s>
<s>
Apple	O
estimated	O
that	O
80%	O
of	O
its	O
dealers	O
sold	O
IBM	O
and	O
Apple	O
computers	O
,	O
and	O
many	O
visitors	O
who	O
were	O
disappointed	O
by	O
the	O
PCjr	O
,	O
or	O
curious	O
about	O
the	O
Macintosh	B-Device
,	O
reportedly	O
left	O
with	O
a	O
IIe	B-Device
instead	O
.	O
</s>
<s>
The	O
PCjr	O
model	O
compared	O
favorably	O
to	O
a	O
IIe	B-Device
also	O
with	O
and	O
no	O
floppy	O
drive	O
,	O
but	O
Apple	O
lowered	O
their	O
computer	O
's	O
price	O
as	O
part	O
of	O
a	O
"	O
Starter	O
System	O
"	O
package	O
,	O
with	O
monitor	O
and	O
floppy	O
drive	O
,	O
to	O
a	O
price	O
as	O
low	O
as	O
,	O
plus	O
a	O
30%	O
discount	O
for	O
the	O
important	O
education	O
market	O
.	O
</s>
<s>
Although	O
the	O
PCjr	O
's	O
CPU	B-Device
was	O
superior	O
,	O
the	O
IIc	O
—	O
which	O
Apple	O
did	O
not	O
describe	O
as	O
a	O
home	O
computer	O
,	O
to	O
avoid	O
the	O
"	O
game	O
machine	O
"	O
connotation	O
—	O
had	O
an	O
excellent	O
keyboard	O
and	O
was	O
compatible	O
with	O
the	O
Apple	B-Device
II	I-Device
's	O
enormous	O
software	O
library	O
.	O
</s>
<s>
An	O
important	O
market	O
was	O
executives	O
who	O
took	O
data	O
home	O
to	O
work	O
on	O
applications	O
such	O
as	O
Lotus	B-Application
1-2-3	I-Application
and	O
Peanut	O
had	O
been	O
rumored	O
to	O
be	O
fully	O
PC	O
compatible	O
,	O
so	O
many	O
customers	O
visited	O
stores	O
believing	O
that	O
the	O
PCjr	O
could	O
run	O
most	O
PC	O
software	O
.	O
</s>
<s>
Thousands	O
of	O
PC	O
applications	O
did	O
require	O
more	O
than	O
128K	O
of	O
memory	O
and	O
two	O
disk	O
drives	O
,	O
making	O
the	O
PCjr	O
incompatible	O
with	O
about	O
60%	O
of	O
software	O
by	O
some	O
measures	O
,	O
including	O
the	O
popular	O
word-processing	O
program	O
WordStar	B-Application
and	O
Lotus	B-Application
1-2-3	I-Application
,	O
common	O
applications	O
used	O
to	O
test	O
PC	O
compatibility	O
.	O
</s>
<s>
ROM	B-Protocol
cartridges	I-Protocol
had	O
small	O
storage	O
capacity	O
,	O
requiring	O
,	O
for	O
instance	O
,	O
two	O
cartridges	B-Protocol
and	O
a	O
floppy	O
disk	O
for	O
the	O
PCjr	O
version	O
of	O
Lotus	B-Application
1-2-3	I-Application
,	O
which	O
also	O
had	O
difficulty	O
fitting	O
complex	O
spreadsheets	O
into	O
128K	O
of	O
RAM	O
.	O
</s>
<s>
IBM	O
published	O
technical	O
details	O
for	O
the	O
PCjr	O
as	O
it	O
had	O
done	O
for	O
the	O
IBM	B-Device
PC	I-Device
to	O
encourage	O
third	O
parties	O
to	O
develop	O
accessories	O
,	O
but	O
did	O
not	O
offer	O
a	O
second	O
floppy	O
drive	O
,	O
hard	O
drive	O
,	O
or	O
memory	O
beyond	O
128KB	O
.	O
</s>
<s>
The	O
PCjr	O
also	O
lacks	O
a	O
DMA	O
controller	O
,	O
so	O
the	O
8088	B-Device
CPU	B-Device
has	O
to	O
service	O
floppy	O
disk	O
transfers	O
directly	O
,	O
causing	O
the	O
system	O
to	O
momentarily	O
freeze	O
while	O
accessing	O
a	O
disk	O
.	O
</s>
<s>
IBM	O
downplayed	O
complaints	O
about	O
the	O
keyboard	O
,	O
but	O
in	O
July	O
announced	O
that	O
it	O
would	O
replace	O
the	O
chiclet	B-Device
keyboards	I-Device
,	O
for	O
free	O
,	O
with	O
a	O
new	O
model	O
with	O
conventional	O
typewriter-style	O
keys	O
.	O
</s>
<s>
They	O
reduced	O
the	O
PCjr	O
's	O
list	O
price	O
,	O
offering	O
a	O
US$999	O
package	O
meant	O
to	O
be	O
superior	O
to	O
the	O
comparably	O
priced	O
Apple	B-Device
IIe	I-Device
and	O
IIc	O
,	O
and	O
they	O
introduced	O
new	O
IBM-made	O
memory	O
expansion	O
options	O
to	O
bring	O
the	O
machine	O
to	O
512KB	O
.	O
</s>
<s>
Advertisements	O
listed	O
the	O
new	O
price	O
,	O
"	O
new	O
typewriter-style	O
keyboard	O
"	O
,	O
standard	O
128KB	O
of	O
memory	O
and	O
expansion	O
options	O
,	O
the	O
PCjr	O
version	O
of	O
1-2-3	O
,	O
and	O
the	O
ability	O
to	O
"	O
run	O
over	O
a	O
thousand	O
of	O
the	O
most	O
popular	O
programs	O
written	O
for	O
the	O
IBM	B-Device
PC	I-Device
"	O
.	O
</s>
<s>
The	O
PCjr	O
reportedly	O
became	O
the	O
best-selling	O
computer	O
,	O
outselling	O
the	O
Apple	B-Device
IIe	I-Device
and	O
IIc	O
by	O
four	O
to	O
one	O
in	O
some	O
stores	O
and	O
even	O
the	O
C64	O
.	O
</s>
<s>
IBM	O
was	O
unable	O
to	O
meet	O
the	O
demand	O
for	O
its	O
new	O
PC	B-Operating_System
AT	I-Operating_System
business	O
microcomputer	O
,	O
but	O
the	O
home-computer	O
market	O
was	O
in	O
decline	O
and	O
the	O
company	O
was	O
likely	O
unable	O
to	O
make	O
a	O
sufficient	O
profit	O
when	O
selling	O
the	O
PCjr	O
at	O
a	O
discount	O
.	O
</s>
<s>
The	O
machine	O
and	O
its	O
many	O
successors	O
sold	O
well	O
,	O
unlike	O
the	O
PCjr	O
,	O
partly	O
because	O
the	O
Tandy	O
1000	O
was	O
sold	O
in	O
ubiquitous	O
Radio	O
Shack	O
stores	O
and	O
partly	O
because	O
it	O
was	O
less	O
costly	O
,	O
easier	O
to	O
expand	O
,	O
and	O
almost	O
entirely	O
compatible	O
with	O
the	O
IBM	B-Device
PC	I-Device
.	O
</s>
<s>
As	O
PC	O
clones	O
became	O
widely	O
available	O
at	O
prices	O
as	O
low	O
as	O
$600	O
,	O
less	O
than	O
the	O
price	O
of	O
the	O
Apple	O
IIc	O
,	O
consumers	O
began	O
purchasing	O
DOS	O
computers	O
for	O
the	O
home	O
in	O
large	O
numbers	O
,	O
and	O
these	O
inexpensive	O
clones	O
succeeded	O
with	O
consumers	O
where	O
the	O
PCjr	O
had	O
failed	O
,	O
by	O
being	O
as	O
fast	O
as	O
,	O
or	O
faster	O
than	O
the	O
IBM	B-Device
PC	I-Device
while	O
still	O
being	O
highly	O
compatible	O
.	O
</s>
<s>
When	O
fully	O
expanded	O
to	O
over	O
600K	O
memory	O
,	O
the	O
PCjr	O
would	O
run	O
most	O
IBM	B-Device
PC	I-Device
software	O
.	O
</s>
<s>
IBM	O
returned	O
to	O
the	O
home	O
market	O
in	O
1990	O
with	O
the	O
PS/1	B-Device
.	O
</s>
<s>
Unlike	O
the	O
PCjr	O
,	O
the	O
PS/1	B-Device
offered	O
full	O
PC	O
compatibility	O
,	O
a	O
low	O
price	O
,	O
and	O
a	O
conventional	O
keyboard	O
.	O
</s>
