<s>
The	O
1801	B-General_Concept
series	I-General_Concept
CPUs	I-General_Concept
were	O
a	O
family	O
of	O
16-bit	B-Device
Soviet	O
microprocessors	B-Architecture
based	O
on	O
the	O
indigenous	O
microarchitecture	B-General_Concept
cores	O
,	O
but	O
binary	O
compatible	O
with	O
DEC	O
's	O
PDP-11	B-Device
machines	O
.	O
</s>
<s>
First	O
released	O
in	O
1980	O
,	O
various	O
models	O
and	O
variants	O
of	O
the	O
series	O
were	O
among	O
the	O
most	O
popular	O
Soviet	O
microprocessors	B-Architecture
and	O
dominated	O
embedded	B-Architecture
systems	I-Architecture
and	O
military	O
applications	O
of	O
the	O
1980s	O
.	O
</s>
<s>
They	O
were	O
also	O
used	O
in	O
widely	O
different	O
areas	O
such	O
as	O
graphing	B-Application
calculators	I-Application
(	O
)	O
and	O
industrial	O
CNCs	O
(	O
Elektronika	O
NC	O
series	O
)	O
,	O
but	O
arguably	O
their	O
most	O
well-known	O
use	O
was	O
in	O
several	O
Soviet	O
general-purpose	O
mini	B-Architecture
-	I-Architecture
and	O
microcomputer	B-Architecture
designs	O
like	O
the	O
SM	B-Device
EVM	I-Device
,	O
DVK	B-Device
,	O
UKNC	B-Device
,	O
and	O
BK	B-Device
families	O
.	O
</s>
<s>
Due	O
to	O
being	O
the	O
CPU	B-Device
of	O
the	O
popular	O
Elektronika	B-Device
BK	I-Device
home	O
computer	O
,	O
used	O
in	O
its	O
late	O
years	O
as	O
a	O
demo	O
machine	O
,	O
as	O
well	O
as	O
the	O
DVK	B-Device
micros	O
that	O
often	O
offered	O
a	O
first	O
glimpse	O
into	O
the	O
UNIX	B-Application
world	O
,	O
this	O
processor	O
achieved	O
something	O
of	O
a	O
cult	O
status	O
among	O
Soviet	O
and	O
then	O
Russian	O
programmers	O
,	O
and	O
to	O
a	O
lesser	O
extent	O
,	O
international	O
programmers	O
.	O
</s>
<s>
The	O
history	O
of	O
this	O
CPU	B-Device
stems	O
from	O
the	O
early	O
1970s	O
,	O
when	O
the	O
group	O
of	O
engineers	O
in	O
Zelenograd	O
's	O
Special	O
Computing	O
Center	O
,	O
led	O
by	O
D.I.	O
</s>
<s>
Yuditsky	O
,	O
developed	O
their	O
first	O
16-bit	B-Device
minicomputer	B-Architecture
,	O
called	O
Elektronika	O
NC-1	O
.	O
</s>
<s>
This	O
machine	O
,	O
intended	O
to	O
directly	O
compete	O
with	O
SM	B-Device
EVM	I-Device
series	O
,	O
was	O
first	O
released	O
in	O
1973	O
and	O
used	O
the	O
bit	B-General_Concept
slice	I-General_Concept
4-bit	O
587	O
CPU	B-Device
,	O
sometimes	O
called	O
the	O
first	O
Soviet	O
microprocessor	B-Architecture
ever	O
.	O
</s>
<s>
However	O
,	O
the	O
bit-slice	B-General_Concept
nature	O
of	O
their	O
CPUs	B-Device
made	O
these	O
machines	O
somewhat	O
unwieldy	O
,	O
especially	O
in	O
military	O
applications	O
,	O
and	O
the	O
need	O
for	O
a	O
single-chip	O
microprocessor	B-Architecture
was	O
identified	O
.	O
</s>
<s>
In	O
1980	O
the	O
first	O
1801	O
CPU	B-Device
intended	O
to	O
fill	O
this	O
niche	O
,	O
K1801VE1	O
,	O
entered	O
production	O
.	O
</s>
<s>
It	O
was	O
essentially	O
a	O
microcontroller	B-Architecture
with	O
256	O
bytes	B-Application
of	O
on-chip	O
RAM	B-Architecture
,	O
2K	O
ROM	B-Device
and	O
other	O
peripheral	O
circuitry	O
,	O
still	O
based	O
on	O
Elektronika	O
NC	O
instruction	B-General_Concept
set	I-General_Concept
,	O
but	O
compatible	O
with	O
a	O
Soviet	O
clone	O
of	O
DEC	O
's	O
Q-Bus	B-Architecture
that	O
was	O
already	O
adopted	O
as	O
an	O
industry	O
standard	O
—	O
a	O
first	O
sign	O
of	O
things	O
to	O
come	O
.	O
</s>
<s>
Its	O
peripheral	O
circuits	O
were	O
underutilized	O
by	O
the	O
industry	O
,	O
as	O
it	O
was	O
mostly	O
used	O
as	O
a	O
general-purpose	O
CPU	B-Device
,	O
rather	O
than	O
a	O
microcontroller	B-Architecture
,	O
so	O
it	O
was	O
decided	O
to	O
simplify	O
the	O
chip	O
,	O
removing	O
unnecessary	O
devices	O
from	O
the	O
die	O
.	O
</s>
<s>
By	O
its	O
nature	O
,	O
Soviet	O
industry	O
was	O
an	O
extremely	O
bureaucratic	B-Application
structure	O
,	O
so	O
decision	O
making	O
process	O
was	O
often	O
driven	O
not	O
by	O
technical	O
or	O
economical	O
considerations	O
,	O
but	O
by	O
the	O
results	O
of	O
the	O
games	O
of	O
influence	O
between	O
various	O
organizations	O
and	O
officials	O
.	O
</s>
<s>
This	O
sudden	O
reorganization	O
resulted	O
in	O
the	O
abandonment	O
of	O
the	O
Elektronika	O
NC	O
architecture	O
(	O
it	O
continued	O
only	O
in	O
CNCs	O
based	O
on	O
an	O
NC-1	O
machine	O
,	O
some	O
of	O
which	O
are	O
used	O
up	O
to	O
this	O
day	O
)	O
and	O
the	O
adoption	O
of	O
the	O
PDP-11	B-Device
compatibility	O
as	O
a	O
MEI	O
standard	O
,	O
a	O
process	O
sometimes	O
called	O
PDP	O
revolt	O
in	O
Russian	O
literature	O
.	O
</s>
<s>
Thus	O
,	O
the	O
microcode	O
for	O
the	O
new	O
simplified	O
CPU	B-Device
was	O
redesigned	O
and	O
made	O
compatible	O
with	O
LSI-11	B-Device
instruction	I-Device
set	I-Device
.	O
</s>
<s>
It	O
was	O
supplemented	O
by	O
the	O
600-gate	O
KR1801VP1	O
(	O
)	O
gate	O
array	O
,	O
which	O
was	O
used	O
to	O
implement	O
various	O
support	O
circuitry	O
,	O
64	O
Kib	O
KR1801RE2	O
ROM	B-Device
chip	I-Device
,	O
and	O
64	O
Kib	O
K573RF3	O
EPROM	B-General_Concept
.	O
</s>
<s>
All	O
CPUs	B-Device
in	O
the	O
family	O
were	O
single-chip	O
16-bit	B-Device
microprocessors	B-Architecture
based	O
on	O
microarchitecture	B-General_Concept
,	O
however	O
only	O
the	O
first	O
one	O
,	O
the	O
K1801VE1	O
microcontroller	B-Architecture
,	O
used	O
the	O
Electronica	O
NC	O
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
Various	O
models	O
differed	O
in	O
clock	O
speed	O
,	O
instruction	B-General_Concept
set	I-General_Concept
(	O
the	O
first	O
models	O
lacked	O
the	O
MUL	O
and	O
DIV	O
commands	O
,	O
for	O
example	O
)	O
,	O
package	O
and	O
address	O
bus	O
width	O
(	O
the	O
latest	O
models	O
supported	O
22-bit	O
addressing	O
)	O
.	O
</s>
<s>
In	O
terms	O
of	O
raw	O
processing	O
power	O
,	O
it	O
is	O
roughly	O
comparable	O
to	O
US-made	O
Intel	B-General_Concept
286	I-General_Concept
.	O
</s>
<s>
They	O
were	O
used	O
in	O
implementing	O
the	O
FIS	O
instruction	O
subset	O
,	O
with	O
instructions	O
processed	O
not	O
in	O
microcode	O
,	O
but	O
as	O
interrupt	O
handlers	O
in	O
shadow	O
ROM	B-Device
.	O
</s>
<s>
DEC	B-Device
PDP-11	I-Device
FPU	B-General_Concept
instructions	O
LDUB	O
,	O
LDSC	O
,	O
STA0	O
,	O
STB0	O
and	O
STQ0	O
have	O
not	O
been	O
implemented	O
.	O
</s>
<s>
All	O
devices	O
in	O
the	O
1806	O
series	O
are	O
manufactured	O
in	O
CMOS	B-Device
technology	O
and	O
require	O
a	O
+5	O
V	O
power	O
supply	O
.	O
</s>
<s>
Microcontroller	B-Architecture
.	O
</s>
<s>
Includes	O
keyboard	B-Device
controller	I-Device
,	O
UART	O
,	O
parallel	O
interface	O
,	O
MMU	B-General_Concept
,	O
watchdog	O
timer	O
and	O
PMU	B-Device
.	O
</s>
<s>
Memory	B-General_Concept
is	O
external	O
.	O
</s>
<s>
All	O
devices	O
in	O
the	O
1836	O
series	O
are	O
manufactured	O
in	O
CMOS	B-Device
technology	O
and	O
require	O
a	O
+5	O
V	O
power	O
supply	O
.	O
</s>
<s>
These	O
CPUs	B-Device
were	O
used	O
in	O
:	O
</s>
