<s>
The	O
HP	B-Device
2100	I-Device
is	O
a	O
series	O
of	O
16-bit	B-Device
minicomputers	B-Architecture
that	O
were	O
produced	O
by	O
Hewlett-Packard	O
(	O
HP	O
)	O
from	O
the	O
mid-1960s	O
to	O
early	O
1990s	O
.	O
</s>
<s>
Tens	O
of	O
thousands	O
of	O
machines	O
in	O
the	O
series	O
were	O
sold	O
over	O
its	O
twenty-five	O
year	O
lifetime	O
,	O
making	O
HP	O
the	O
fourth	O
largest	O
minicomputer	B-Architecture
vendor	O
during	O
the	O
1970s	O
.	O
</s>
<s>
All	O
of	O
these	O
models	O
were	O
replaced	O
by	O
the	O
HP	B-Device
2100	I-Device
series	O
in	O
1971	O
,	O
and	O
then	O
again	O
as	O
the	O
21MX	O
series	O
in	O
1974	O
when	O
the	O
magnetic-core	O
memory	O
was	O
replaced	O
with	O
semiconductor	O
memory	O
.	O
</s>
<s>
All	O
of	O
these	O
models	O
were	O
also	O
packaged	O
as	O
the	O
HP	O
2000	O
series	O
,	O
combining	O
a	O
2100-series	O
machine	O
with	O
optional	O
components	O
in	O
order	O
to	O
run	O
the	O
BASIC	O
programming	O
language	O
in	O
a	O
multi-user	O
time	B-General_Concept
sharing	I-General_Concept
fashion	O
.	O
</s>
<s>
HP	B-Language
Time-Shared	I-Language
BASIC	I-Language
was	O
popular	O
in	O
the	O
1970s	O
,	O
and	O
many	O
early	O
BASIC	O
programs	O
were	O
written	O
on	O
or	O
for	O
the	O
platform	O
,	O
most	O
notably	O
the	O
seminal	O
Star	B-Application
Trek	I-Application
that	O
was	O
popular	O
during	O
the	O
early	O
home	O
computer	O
era	O
.	O
</s>
<s>
The	O
introduction	O
of	O
the	O
HP	B-Device
3000	I-Device
in	O
1974	O
provided	O
high-end	O
competition	O
to	O
the	O
2100	O
series	O
;	O
the	O
entire	O
line	O
was	O
renamed	O
as	O
the	O
HP	B-Device
1000	I-Device
in	O
1977	O
and	O
positioned	O
as	O
real-time	B-General_Concept
computers	O
.	O
</s>
<s>
A	O
greatly	O
redesigned	O
version	O
was	O
introduced	O
in	O
1979	O
as	O
the	O
1000	O
L-Series	O
,	O
using	O
CMOS	B-Device
large	O
scale	O
integration	O
chips	O
and	O
introducing	O
a	O
desk-side	O
tower	B-General_Concept
case	I-General_Concept
model	O
.	O
</s>
<s>
In	O
1964	O
,	O
Kay	O
Magleby	O
and	O
Paul	O
Stoft	O
began	O
experimenting	O
with	O
the	O
use	O
of	O
PDP-5	B-Device
and	O
PDP-8	B-Device
computers	O
to	O
act	O
as	O
controllers	O
for	O
their	O
complex	O
test	O
systems	O
,	O
but	O
they	O
felt	O
the	O
machines	O
would	O
require	O
changes	O
to	O
truly	O
suit	O
their	O
needs	O
.	O
</s>
<s>
Bill	O
Hewlett	O
initially	O
refused	O
to	O
consider	O
the	O
development	O
of	O
a	O
"	O
minicomputer	B-Architecture
"	O
,	O
but	O
when	O
Packard	O
reframed	O
it	O
as	O
an	O
"	O
instrument	O
controller	O
"	O
the	O
deal	O
was	O
approved	O
.	O
</s>
<s>
It	O
was	O
one	O
of	O
the	O
earliest	O
16-bit	B-Device
minis	O
to	O
hit	O
the	O
market	O
,	O
but	O
at	O
the	O
time	O
it	O
was	O
more	O
notable	O
as	O
"	O
an	O
unusual	O
new	O
instrumentation	O
computer	O
"	O
with	O
a	O
highly	O
expandable	O
design	O
and	O
real-time	B-General_Concept
support	O
.	O
</s>
<s>
An	O
additional	O
set	O
added	O
input/output	B-General_Concept
devices	I-General_Concept
like	O
tape	O
drives	O
,	O
printers	O
,	O
punched	B-Architecture
cards	I-Architecture
and	O
paper	O
tape	O
and	O
other	O
peripherals	O
.	O
</s>
<s>
Real-time	B-General_Concept
service	O
was	O
provided	O
by	O
having	O
each	O
card	O
slot	O
be	O
assigned	O
a	O
fixed	O
interrupt	B-General_Concept
vector	I-General_Concept
that	O
called	O
the	O
appropriate	O
device	B-Application
driver	I-Application
.	O
</s>
<s>
As	O
the	O
machine	O
entered	O
the	O
market	O
,	O
it	O
quickly	O
became	O
clear	O
it	O
was	O
selling	O
much	O
more	O
rapidly	O
into	O
the	O
business	O
data	B-General_Concept
processing	I-General_Concept
market	O
than	O
the	O
originally	O
targeted	O
instrumentation	O
market	O
.	O
</s>
<s>
Chassis	O
includes	O
16	O
I/O	B-General_Concept
slots	O
,	O
also	O
expandable	O
.	O
</s>
<s>
2115A	O
,	O
short-lived	O
cost-reduced	O
version	O
that	O
removed	O
the	O
DMA	O
and	O
some	O
math	O
functions	O
,	O
had	O
only	O
8	O
I/O	B-General_Concept
slots	O
,	O
and	O
ran	O
at	O
8MHz	O
clock	O
and	O
a	O
2.0	O
µs	O
cycle	O
time	O
.	O
</s>
<s>
This	O
was	O
based	O
on	O
the	O
2116B	O
(	O
a	O
2116A	O
with	O
an	O
expanded	O
8k	O
core	O
memory	O
)	O
running	O
HP	B-Language
Time-Shared	I-Language
BASIC	I-Language
and	O
used	O
a	O
separate	O
2114	O
as	O
a	O
terminal	B-Device
server	I-Device
.	O
</s>
<s>
Some	O
models	O
used	O
low-end	O
versions	O
of	O
the	O
same	O
CPU	O
as	O
the	O
terminal	B-Device
server	I-Device
;	O
the	O
2000F	O
,	O
for	O
instance	O
,	O
used	O
a	O
2100S	O
as	O
the	O
main	O
CPU	O
and	O
primary	O
storage	O
controller	O
,	O
while	O
a	O
2100A	O
acted	O
as	O
the	O
terminal	B-Device
server	I-Device
.	O
</s>
<s>
In	O
the	O
last	O
version	O
,	O
the	O
2000F	O
,	O
a	O
2100S	O
and	O
2100A	O
CPU	O
were	O
used	O
,	O
with	O
the	O
2100A	O
connected	O
to	O
up	O
to	O
32	O
serial	B-General_Concept
terminals	I-General_Concept
via	O
serial	O
multiplexer	O
interfaces	O
.	O
</s>
<s>
In	O
spite	O
of	O
its	O
relatively	O
high	O
costs	O
—	O
the	O
2000F	O
cost	O
$	O
105,000	O
in	O
1974	O
,	O
or	O
about	O
$	O
in	O
—	O
it	O
was	O
the	O
first	O
minicomputer	B-Architecture
to	O
offer	O
time-shared	B-General_Concept
BASIC	O
,	O
which	O
made	O
it	O
very	O
popular	O
in	O
the	O
early-to-mid	O
1970s	O
.	O
</s>
<s>
However	O
,	O
the	O
CPU	O
was	O
rebuilt	O
with	O
microcode	B-Device
that	O
could	O
be	O
user-programmed	O
,	O
added	O
hardware	O
multiply	O
and	O
divide	O
,	O
and	O
it	O
added	O
a	O
simple	O
memory	B-General_Concept
protection	I-General_Concept
system	O
,	O
which	O
caused	O
a	O
high-priority	O
interrupt	O
when	O
triggered	O
.	O
</s>
<s>
A	O
two-channel	O
DMA	B-General_Concept
controller	I-General_Concept
provided	O
higher	O
throughput	O
.	O
</s>
<s>
An	O
optional	O
floating-point	B-General_Concept
unit	I-General_Concept
was	O
also	O
available	O
.	O
</s>
<s>
That	O
year	O
,	O
they	O
merged	O
the	O
Mountain	O
View	O
Division	O
,	O
which	O
made	O
magnetic	B-Architecture
tape	I-Architecture
drives	I-Architecture
,	O
with	O
the	O
Cupertino	O
Division	O
to	O
create	O
the	O
Data	O
Systems	O
Division	O
(	O
DSD	O
)	O
.	O
</s>
<s>
By	O
this	O
time	O
,	O
the	O
HP	B-Device
3000	I-Device
project	O
was	O
in	O
serious	O
trouble	O
,	O
and	O
in	O
February	O
1973	O
,	O
Packard	O
sent	O
Paul	O
Ely	O
to	O
take	O
over	O
the	O
division	O
.	O
</s>
<s>
2100A	O
,	O
normally	O
with	O
4kW	O
but	O
expandable	O
to	O
32kW	O
,	O
14	O
I/O	B-General_Concept
slots	O
expandable	O
to	O
45	O
.	O
</s>
<s>
In	O
1972	O
,	O
the	O
division	O
decided	O
to	O
move	O
to	O
4kbit	O
SRAM	B-Architecture
memory	O
chips	O
in	O
place	O
of	O
core	O
.	O
</s>
<s>
At	O
the	O
time	O
they	O
made	O
this	O
decision	O
,	O
4kbit	O
SRAMs	O
were	O
not	O
actually	O
available	O
,	O
so	O
experimental	O
machines	O
using	O
the	O
core	O
from	O
a	O
2100	O
series	O
were	O
used	O
initially	O
,	O
replaced	O
by	O
1kbit	O
SRAM	B-Architecture
.	O
</s>
<s>
The	O
21MX	O
series	O
featured	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
and	O
semiconductor	O
memory	O
expandable	O
to	O
1,048,576	O
words	O
(	O
one	O
megaword	O
)	O
.	O
</s>
<s>
The	O
21MX	O
ran	O
the	O
HP	O
RTE	O
(	O
Real	O
Time	O
)	O
Operating	B-General_Concept
System	I-General_Concept
(	O
OS	O
)	O
.	O
</s>
<s>
They	O
started	O
out	O
as	O
refrigerator-sized	O
19-inch	B-Application
rackmount	I-Application
systems	I-Application
with	O
lights	O
and	O
switches	O
on	O
the	O
front	O
panels	O
.	O
</s>
<s>
The	O
last	O
models	O
would	O
use	O
a	O
1-chip	O
processor	O
and	O
fit	O
under	O
a	O
desk	O
using	O
a	O
console	B-General_Concept
terminal	I-General_Concept
rather	O
than	O
a	O
front	O
panel	O
.	O
</s>
<s>
Despite	O
customer	O
demands	O
for	O
a	O
real-time	B-General_Concept
ability	O
and	O
HP	O
D	O
's	O
efforts	O
using	O
an	O
installable	O
real-time	B-General_Concept
card	O
,	O
the	O
RTE-A	O
OS	O
was	O
not	O
as	O
good	O
at	O
real-time	B-General_Concept
operations	O
as	O
RTE	O
on	O
a	O
21MX	O
.	O
</s>
<s>
Many	O
companies	O
use	O
real-time	B-General_Concept
operations	O
to	O
take	O
a	O
measurements	O
and	O
control	O
processes	O
—	O
turn	O
on	O
or	O
off	O
a	O
pump	O
,	O
heater	O
,	O
a	O
valve	O
,	O
speed	O
up	O
or	O
slow	O
down	O
a	O
motor	O
,	O
etc	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
1977	O
,	O
the	O
entire	O
line	O
was	O
renamed	O
as	O
the	O
"	O
HP	B-Device
1000	I-Device
"	O
,	O
becoming	O
the	O
"	O
HP	B-Device
1000	I-Device
M-Series	O
"	O
and	O
"	O
HP	B-Device
1000	I-Device
E-Series	O
"	O
.	O
</s>
<s>
The	O
next	O
year	O
the	O
"	O
HP	B-Device
1000	I-Device
F-Series	O
"	O
was	O
introduced	O
,	O
which	O
was	O
an	O
E-Series	O
with	O
an	O
added	O
floating	B-General_Concept
point	I-General_Concept
unit	I-General_Concept
.	O
</s>
<s>
By	O
1978	O
,	O
the	O
success	O
of	O
the	O
line	O
had	O
propelled	O
HP	O
to	O
become	O
the	O
fourth	O
largest	O
manufacturer	O
in	O
the	O
minicomputer	B-Architecture
space	O
,	O
trailing	O
only	O
DEC	O
,	O
IBM	O
,	O
and	O
Data	O
General	O
.	O
</s>
<s>
In	O
1980	O
,	O
the	O
"	O
HP	B-Device
1000	I-Device
L-Series	O
"	O
was	O
introduced	O
.	O
</s>
<s>
This	O
used	O
a	O
new	O
processor	O
based	O
on	O
HP	O
's	O
large	O
scale	O
integration	O
silicon	B-Algorithm
on	I-Algorithm
sapphire	I-Algorithm
process	O
.	O
</s>
<s>
Additionally	O
,	O
the	O
expansion	O
cards	O
were	O
also	O
equipped	O
with	O
their	O
own	O
processors	O
that	O
allowed	O
them	O
to	O
access	O
main	O
memory	O
and	O
conduct	O
input/output	B-General_Concept
without	O
bothering	O
the	O
CPU	O
.	O
</s>
<s>
These	O
models	O
lacked	O
the	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
.	O
</s>
<s>
The	O
L-Series	O
was	O
,	O
in	O
turn	O
,	O
replaced	O
in	O
1982	O
with	O
the	O
"	O
HP	B-Device
1000	I-Device
A-Series	O
"	O
,	O
which	O
included	O
a	O
new	O
"	O
Lightning	O
"	O
CPU	O
design	O
that	O
reached	O
1MIPS	O
,	O
and	O
the	O
even	O
faster	O
"	O
Magic	O
"	O
CPU	O
at	O
3MIPS	O
.	O
</s>
<s>
A	O
wide	O
variety	O
of	O
different	O
models	O
was	O
produced	O
,	O
including	O
desk-side	O
towers	O
,	O
and	O
a	O
variety	O
of	O
different	O
size	O
rack-mount	B-Application
systems	O
.	O
</s>
<s>
A600+	O
—	O
based	O
on	O
Am2900	B-General_Concept
bit-slice	B-General_Concept
processor	I-General_Concept
,	O
supports	O
code	O
and	O
data	O
separation	O
,	O
optional	O
ECC	O
(	O
error	O
correcting	O
)	O
memory	O
.	O
</s>
<s>
A700	O
—	O
based	O
on	O
AMD	B-General_Concept
AM2903	I-General_Concept
bit-slice	B-General_Concept
processor	I-General_Concept
,	O
optional	O
hardware	O
floating	B-General_Concept
point	I-General_Concept
processor	I-General_Concept
,	O
1MIPS	O
,	O
204kFLOPS	O
,	O
microprogramming	B-Device
,	O
optional	O
ECC	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
A900	O
—	O
Provides	O
pipelined	B-General_Concept
data	O
path	O
,	O
3MIPS	O
,	O
500kFLOPS	O
,	O
ECC	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
A400	O
—	O
first	O
single-board	O
CPU	O
including	O
4	O
serial	O
lines	O
;	O
CPU	O
fabricated	O
by	O
VLSI	O
Technology	O
with	O
their	O
CMOS-40	O
process	O
,	O
512	O
KB	O
RAM	O
on	O
board	O
.	O
</s>
<s>
A990	O
—	O
CPU	O
implemented	O
with	O
two	O
208-pin	O
CMOS	B-Device
application-specific	O
integrated	O
circuits	O
(	O
ASICs	O
)	O
,	O
298	O
instructions	O
,	O
supports	O
up	O
to	O
512	O
MB	O
of	O
memory	O
.	O
</s>
<s>
+	O
HP	O
MiniComputers	B-Architecture
Year	O
Machine	O
MicrowordSize	O
MicrocodeSize	O
Microword	O
Types	O
ALU	O
CarryGenerator	O
MicroSequencer	O
1973	O
2100S	O
24	O
1K	O
3	O
4×74181	O
74182	O
Discrete	O
1974	O
1000	O
M-Series	O
24	O
4K	O
4	O
4×74181	O
74182	O
Discrete	O
1976	O
1000	O
E-Series	O
24	O
16K	O
4	O
4×74S181	O
74S182	O
Discrete	O
1978	O
1000	O
F-Series	O
24	O
16K	O
4	O
4×74S181	O
74S182	O
Discrete	O
19	O
??	O
</s>
<s>
Custom	O
CMOS/SOS	O
1981	O
1000	O
A600	O
56	O
4K	O
5	O
4×2901B	O
74S182	O
2910+2904	O
1982	O
1000	O
A700	O
32	O
16K	O
11	O
4×2903	O
74S182	O
2911	O
1984	O
1000	O
A900	O
48	O
32K	O
4	O
4×74S381	O
74S182	O
Discrete	O
1986	O
1000	O
A400	O
32	O
16K	O
11	O
Custom	O
CMOS/SOS	O
1975	O
13037	O
Controller	O
24	O
4K	O
7	O
4×74S181	O
74S182	O
Discrete	O
1980	O
13365	O
Controller	O
24	O
3K	O
?	O
</s>
<s>
1977	O
3000	B-Device
Series	O
I	O
32	O
4K	O
5	O
4×74181	O
74182	O
Discrete	O
1978	O
3000	B-Device
Series	O
III	O
32	O
64K	O
5	O
4×74S181	O
74S182	O
Discrete	O
1978	O
3000	B-Device
Series	O
33	O
32	O
6K	O
?	O
</s>
<s>
Custom	O
CMOS/SOS	O
198	O
?	O
</s>
<s>
3000	B-Device
Series	O
48	O
48	O
12K	O
2	O
4×74S181	O
74S182	O
Discrete	O
1982	O
3000	B-Device
Series	O
64	O
64	O
8K	O
?	O
</s>
<s>
4×	O
100181	O
100179	O
Discrete	O
1985	O
3000	B-Device
Series	O
37	O
64	O
10K	O
?	O
</s>
<s>
Notable	O
among	O
these	O
was	O
Mike	B-Application
Mayfield	I-Application
's	O
Star	B-Application
Trek	I-Application
of	O
1971	O
.	O
</s>
<s>
The	O
HP	B-Device
2100	I-Device
was	O
designed	O
in	O
an	O
era	O
when	O
RAM	O
in	O
the	O
form	O
of	O
magnetic	O
core	O
memory	O
was	O
falling	O
from	O
dollars	O
to	O
pennies	O
per	O
bit	O
,	O
while	O
implementing	O
processor	B-General_Concept
registers	I-General_Concept
using	O
transistors	O
or	O
small-scale	O
integration	O
remained	O
very	O
expensive	O
.	O
</s>
<s>
This	O
favored	O
designs	O
with	O
few	O
registers	O
and	O
most	O
storage	O
in	O
RAM	O
,	O
which	O
in	O
turn	O
influenced	O
the	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
to	O
use	O
a	O
memory-memory	O
or	O
memory-accumulator	O
design	O
.	O
</s>
<s>
This	O
basic	O
concept	O
was	O
first	O
widely	O
introduced	O
in	O
the	O
seminal	O
12-bit	O
PDP-8	B-Device
,	O
which	O
spawned	O
many	O
similar	O
designs	O
like	O
the	O
2100	O
.	O
</s>
<s>
In	O
the	O
2100	O
,	O
addresses	O
are	O
15-bits	O
long	O
,	O
allowing	O
a	O
total	O
of	O
32k	O
16-bit	B-Device
words	O
of	O
memory	O
(	O
64	O
KB	O
in	O
modern	O
terms	O
)	O
.	O
</s>
<s>
The	O
smallest	O
addressable	O
unit	O
of	O
memory	O
is	O
a	O
16-bit	B-Device
word	O
,	O
there	O
are	O
no	O
instructions	O
that	O
fetch	O
a	O
single	O
8-bit	O
byte	O
.	O
</s>
<s>
The	O
two	O
most	O
significant	O
bits	O
are	O
used	O
to	O
implement	O
memory	B-General_Concept
protection	I-General_Concept
.	O
</s>
<s>
This	O
means	O
that	O
one	O
can	O
load	O
a	O
value	O
into	O
an	O
accumulator	B-General_Concept
using	O
the	O
normal	O
register-save	O
operation	O
,	O
for	O
instance	O
,	O
LDA	O
1	O
will	O
LoaD	O
the	O
value	O
of	O
the	O
A	O
register	O
into	O
memory	O
location	O
1	O
,	O
thereby	O
copying	O
the	O
value	O
of	O
A	O
into	O
B	O
.	O
</s>
<s>
The	O
P	O
register	O
is	O
used	O
as	O
the	O
program	B-General_Concept
counter	I-General_Concept
and	O
automatically	O
incremented	O
with	O
every	O
instruction	O
,	O
but	O
it	O
is	O
also	O
used	O
as	O
the	O
base	O
address	O
for	O
some	O
memory	O
accesses	O
(	O
see	O
below	O
)	O
that	O
are	O
calculated	O
and	O
placed	O
in	O
M	O
.	O
There	O
are	O
also	O
two	O
one-bit	O
registers	O
,	O
Overflow	O
and	O
Extend	O
,	O
in	O
modern	O
terms	O
,	O
these	O
bits	O
would	O
be	O
considered	O
the	O
status	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
Additionally	O
,	O
there	O
is	O
the	O
16-bit	B-Device
S/D	O
(	O
Switch/Display	O
)	O
register	O
,	O
which	O
is	O
used	O
for	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
from	O
the	O
front	O
panel	O
.	O
</s>
<s>
Certain	O
areas	O
of	O
memory	O
are	O
reserved	O
for	O
special	O
purposes	O
,	O
like	O
locations	O
0	O
and	O
1	O
used	O
by	O
the	O
accumulators	B-General_Concept
.	O
</s>
<s>
Additional	O
words	O
in	O
the	O
lowest	O
64-locations	O
in	O
memory	O
are	O
used	O
for	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
,	O
and	O
vectored	B-Architecture
interrupts	I-Architecture
(	O
see	O
below	O
)	O
.	O
</s>
<s>
The	O
original	O
instruction	B-General_Concept
set	I-General_Concept
contained	O
68	O
or	O
70	O
instructions	O
.	O
</s>
<s>
All	O
68	O
instructions	O
in	O
the	O
standard	O
instruction	B-General_Concept
set	I-General_Concept
are	O
16	B-Device
bits	I-Device
long	O
.	O
</s>
<s>
Conditional	B-General_Concept
branching	I-General_Concept
is	O
done	O
with	O
a	O
conditional	O
skip-over-one	O
instruction	O
,	O
that	O
one	O
instruction	O
normally	O
being	O
a	O
jump	B-General_Concept
instruction	I-General_Concept
.	O
</s>
<s>
There	O
is	O
no	O
stack	B-Application
for	O
subroutines	O
;	O
instead	O
,	O
the	O
first	O
memory	O
location	O
of	O
the	O
routine	O
is	O
reserved	O
,	O
and	O
the	O
return	O
address	O
written	O
to	O
that	O
location	O
by	O
the	O
JSB	O
instruction	O
.	O
</s>
<s>
This	O
means	O
there	O
is	O
no	O
internal	O
support	O
for	O
re-entrant	B-Operating_System
code	I-Operating_System
;	O
support	O
for	O
this	O
has	O
to	O
be	O
added	O
via	O
a	O
user	O
implemented	O
stack	B-Application
.	O
</s>
<s>
There	O
are	O
three	O
basic	O
styles	O
of	O
instructions	O
in	O
the	O
ISA	O
;	O
memory	O
references	O
,	O
register	O
references	O
,	O
and	O
input/output	B-General_Concept
.	O
</s>
<s>
Certain	O
models	O
extended	O
the	O
ISA	O
with	O
add-on	O
hardware	O
,	O
adding	O
,	O
for	O
instance	O
,	O
floating	B-General_Concept
point	I-General_Concept
instructions	O
or	O
additional	O
integer	O
math	O
and	O
memory	O
instructions	O
,	O
but	O
these	O
would	O
fall	O
into	O
the	O
same	O
three	O
basic	O
categories	O
.	O
</s>
<s>
Memory	O
instructions	O
use	O
four	O
bits	O
for	O
the	O
instruction	O
,	O
and	O
two	O
more	O
for	O
special	O
flags	O
,	O
for	O
a	O
total	O
of	O
six	O
bits	O
of	O
the	O
16-bit	B-Device
word	O
.	O
</s>
<s>
The	O
second	O
group	O
has	O
eight	O
instructions	O
that	O
perform	O
increments	O
on	O
the	O
registers	O
and	O
then	O
a	O
conditional	B-General_Concept
branch	I-General_Concept
.	O
</s>
<s>
Input/Output	B-General_Concept
instructions	O
normally	O
communicate	O
through	O
the	O
accumulators	B-General_Concept
.	O
</s>
<s>
The	O
instruction	O
format	O
starts	O
with	O
the	O
bits	O
"	O
1000	O
"	O
in	O
the	O
most	O
significant	O
bits	O
,	O
followed	O
by	O
a	O
single	O
bit	O
indicating	O
which	O
register	O
to	O
use	O
(	O
A	O
=	O
0	O
,	O
B	O
=	O
1	O
)	O
,	O
followed	O
by	O
a	O
"	O
1	O
"	O
,	O
the	O
H/C	O
flag	O
bit	O
,	O
and	O
then	O
three	O
bits	O
for	O
the	O
instruction	O
and	O
the	O
remaining	O
six	O
bits	O
for	O
the	O
I/O	B-General_Concept
device	I-General_Concept
ID	O
,	O
or	O
channel	O
,	O
allowing	O
up	O
to	O
64	O
devices	O
.	O
</s>
<s>
I/O	B-General_Concept
is	O
initiated	O
by	O
clearing	O
the	O
Flag	O
bit	O
with	O
STF	O
and	O
then	O
setting	O
the	O
C	O
bit	O
using	O
STC	O
.	O
</s>
<s>
Location	O
4	O
through	O
7	O
are	O
hard-wired	O
to	O
power	O
failures	O
,	O
parity	O
check	O
errors	O
,	O
and	O
in	O
later	O
models	O
memory	B-General_Concept
protection	I-General_Concept
errors	O
.	O
</s>
<s>
Locations	O
8	O
and	O
up	O
are	O
user-accessible	O
interrupt	B-General_Concept
vectors	I-General_Concept
,	O
mapped	O
to	O
an	O
I/O	B-General_Concept
channel	O
and	O
arranged	O
in	O
priority	O
order	O
.	O
</s>
<s>
So	O
if	O
I/O	B-General_Concept
device	I-General_Concept
13	O
produced	O
an	O
interrupt	O
,	O
the	O
CPU	O
jumps	O
to	O
the	O
location	O
in	O
memory	O
location	O
13	O
,	O
but	O
only	O
if	O
it	O
is	O
not	O
masked	O
out	O
by	O
a	O
higher-priority	O
interrupt	O
,	O
1	O
to	O
12	O
.	O
</s>
<s>
Another	O
key	O
feature	O
of	O
the	O
2100	O
series	O
is	O
a	O
separate	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
controller	O
that	O
uses	O
cycle	B-General_Concept
stealing	I-General_Concept
to	O
access	O
memory	O
when	O
the	O
CPU	O
is	O
not	O
using	O
it	O
,	O
during	O
the	O
times	O
when	O
it	O
is	O
performing	O
internal	O
calculations	O
for	O
instance	O
.	O
</s>
<s>
Using	O
this	O
feature	O
,	O
lengthy	O
I/O	B-General_Concept
processes	O
can	O
be	O
completed	O
while	O
the	O
CPU	O
works	O
on	O
other	O
problems	O
.	O
</s>
<s>
The	O
system	O
is	O
set	O
up	O
by	O
sending	O
an	O
instruction	O
to	O
the	O
DMA	B-General_Concept
controller	I-General_Concept
using	O
the	O
I/O	B-General_Concept
commands	O
;	O
the	O
DMA	B-General_Concept
controller	I-General_Concept
is	O
channel	O
6	O
,	O
and	O
is	O
initially	O
sent	O
an	O
instruction	O
containing	O
the	O
number	O
of	O
the	O
I/O	B-General_Concept
device	I-General_Concept
that	O
wants	O
to	O
use	O
DMA	O
,	O
whether	O
it	O
is	O
an	O
input	O
(	O
write	O
to	O
memory	O
from	O
device	O
)	O
or	O
output	O
(	O
read	O
from	O
memory	O
to	O
device	O
)	O
,	O
the	O
starting	O
location	O
in	O
memory	O
for	O
the	O
data	O
,	O
and	O
the	O
number	O
of	O
words	O
.	O
</s>
<s>
This	O
setup	O
code	O
is	O
often	O
installed	O
into	O
one	O
of	O
the	O
interrupt	B-General_Concept
vectors	I-General_Concept
,	O
automating	O
the	O
process	O
.	O
</s>
<s>
HP	O
supplied	O
a	O
three-pass	O
assembler	B-Language
for	O
the	O
machine	O
,	O
using	O
a	O
column-delimited	O
format	O
.	O
</s>
<s>
The	O
assembler	B-Language
allows	O
basic	O
mathematical	O
expressions	O
to	O
be	O
written	O
directly	O
,	O
instead	O
of	O
using	O
mnemonics	O
,	O
and	O
also	O
includes	O
a	O
number	O
of	O
pseudo-instructions	O
like	O
ORG	O
to	O
set	O
the	O
base	O
address	O
of	O
the	O
program	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
assembler	B-Language
and	O
associated	O
linker	B-Application
,	O
the	O
machines	O
initially	O
shipped	O
with	O
a	O
FORTRAN	O
66	O
compiler	B-Language
,	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
I/O	B-General_Concept
drivers	O
.	O
</s>
<s>
Over	O
time	O
,	O
additional	O
languages	O
were	O
added	O
including	O
BASIC	O
,	O
ALGOL	B-Language
,	O
FORTRAN	O
IV	O
and	O
FORTRAN	O
77	O
.	O
</s>
<s>
HP	O
ported	O
implementations	O
of	O
AGL	O
to	O
the	O
platform	O
,	O
which	O
added	O
commands	O
to	O
their	O
BASIC	O
to	O
produce	O
graphics	O
on	O
their	O
graphics	O
terminals	B-General_Concept
and	O
plotters	B-Operating_System
.	O
</s>
<s>
The	O
2100s	O
were	O
normally	O
used	O
with	O
the	O
"	O
Real	O
Time	O
Executive	O
"	O
operating	B-General_Concept
system	I-General_Concept
,	O
or	O
RTE	O
for	O
short	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
shell	O
,	O
even	O
in	O
the	O
late	O
1970s	O
,	O
was	O
very	O
primitive	O
,	O
with	O
a	O
single-level	O
file	B-Application
system	I-Application
,	O
File	O
Manager	O
,	O
or	O
FMGR	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
command	O
to	O
run	O
a	O
FORTRAN	O
compiler	B-Language
would	O
be	O
as	O
follows	O
:	O
</s>
<s>
The	O
HP	B-Device
1000	I-Device
also	O
was	O
one	O
of	O
the	O
few	O
minicomputers	B-Architecture
that	O
restricted	O
file	O
names	O
to	O
only	O
five	O
characters	O
,	O
rather	O
than	O
the	O
six	O
common	O
at	O
the	O
time	O
,	O
which	O
made	O
porting	O
and	O
even	O
writing	O
programs	O
a	O
challenge	O
.	O
</s>
<s>
The	O
later	O
RTE-A	O
for	O
HP	B-Device
1000	I-Device
provided	O
conventional	O
directory	O
structure	O
with	O
16.4	O
file	O
names	O
,	O
and	O
made	O
the	O
ru	O
command	O
optional	O
.	O
</s>
<s>
TODS	O
(	O
Test	O
Oriented	O
Disk	B-Device
System	O
)	O
was	O
developed	O
by	O
a	O
technician	O
at	O
the	O
HP	O
board	O
repair	O
center	O
to	O
improve	O
turn-around	O
time	O
in	O
the	O
center	O
.	O
</s>
<s>
There	O
was	O
also	O
MTOS	O
(	O
Magnetic	O
Tape	O
Operating	B-General_Concept
System	I-General_Concept
)	O
similar	O
to	O
TODS	O
.	O
</s>
<s>
The	O
HP	B-Device
9810	I-Device
,	O
9820	O
and	O
9830	B-Device
desktop	O
computers	O
use	O
a	O
slow	O
,	O
serialized	O
TTL	B-General_Concept
version	O
of	O
the	O
2116	O
CPU	O
,	O
although	O
they	O
did	O
not	O
ultimately	O
use	O
any	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
or	O
application	O
software	O
,	O
instead	O
relying	O
on	O
user-friendly	O
ROM-based	O
interpreters	B-Application
,	O
such	O
as	O
BASIC	O
,	O
which	O
work	O
when	O
powered	O
up	O
and	O
integrated	O
keyboards	O
and	O
displays	O
rather	O
than	O
disks	B-Device
or	O
standard	O
terminals	B-General_Concept
.	O
</s>
<s>
In	O
1975	O
,	O
HP	O
introduced	O
the	O
BPC	O
,	O
one	O
of	O
the	O
world	O
's	O
first	O
16-bit	B-Device
microprocessors	B-Architecture
,	O
using	O
HP	O
's	O
NMOS-II	O
process	O
.	O
</s>
<s>
The	O
BPC	O
was	O
usually	O
packaged	O
in	O
a	O
ceramic	O
hybrid	O
module	O
with	O
the	O
EMC	O
and	O
IOC	O
chips	O
,	O
which	O
added	O
extended	O
math	O
and	O
I/O	B-General_Concept
instructions	O
.	O
</s>
<s>
The	O
later	O
9845	O
workstation	O
added	O
an	O
MMU	B-General_Concept
chip	O
.	O
</s>
<s>
These	O
were	O
the	O
forerunners	O
of	O
personal	B-Device
computers	I-Device
and	O
technical	O
workstations	O
.	O
</s>
<s>
The	O
major	O
differences	O
between	O
the	O
original	O
2116	O
architecture	O
and	O
the	O
BPC	O
microprocessor	B-Architecture
are	O
a	O
completely	O
redesigned	O
I/O	B-General_Concept
structure	O
,	O
the	O
removal	O
of	O
multiple	O
levels	O
of	O
indirect	O
addressing	O
,	O
and	O
the	O
provision	O
of	O
a	O
stack	B-Application
register	O
for	O
subroutine	O
call	O
and	O
return	O
.	O
</s>
<s>
The	O
elimination	O
of	O
multiple	O
indirection	O
made	O
an	O
additional	O
bit	O
available	O
in	O
a	O
memory	O
word	O
containing	O
an	O
indirect	O
address	O
,	O
allowing	O
the	O
maximum	O
memory	O
capacity	O
to	O
be	O
increased	O
from	O
32K	O
16-bit	B-Device
words	O
to	O
64K	O
.	O
</s>
<s>
The	O
BPC	O
also	O
added	O
an	O
input	O
allowing	O
the	O
"	O
current	O
page	O
"	O
to	O
be	O
relative	O
to	O
the	O
location	O
of	O
the	O
current	B-General_Concept
instruction	I-General_Concept
,	O
rather	O
than	O
a	O
power-of-two	O
aligned	O
page	O
.	O
</s>
<s>
Czechoslovakia	O
produced	O
its	O
own	O
HP	B-Device
1000	I-Device
compatible	O
clones	O
,	O
designated	O
ADT4000	O
(	O
4300	O
,	O
4500	O
,	O
4700	O
,	O
4900	O
)	O
.	O
</s>
<s>
Those	O
computers	O
served	O
in	O
power	O
plants	O
,	O
including	O
nuclear	O
ones	O
,	O
other	O
industry	O
,	O
military	O
,	O
at	O
universities	O
,	O
etc.	O
,	O
for	O
their	O
high	O
reliability	O
and	O
real-time	B-General_Concept
features	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
were	O
DOS/ADT	O
(	O
several	O
versions	O
)	O
and	O
Unix	O
.	O
</s>
<s>
The	O
ADT	O
4900	O
was	O
designed	O
as	O
a	O
single-board	B-Device
computer	I-Device
,	O
but	O
its	O
mass	O
production	O
did	O
not	O
start	O
.	O
</s>
<s>
Czechoslovak	O
People	O
's	O
Army	O
used	O
ADT	O
based	O
MOMI	O
1	O
and	O
MOMI	O
2	O
mobile	O
minicomputers	B-Architecture
,	O
built	O
into	O
a	O
container	O
carried	O
by	O
the	O
Tatra	O
148	O
truck	O
.	O
</s>
