<s>
ES	B-Device
PEVM	I-Device
( ЕС	O
ПЭВМ	O
)	O
was	O
a	O
Soviet	O
clone	B-General_Concept
of	O
the	O
IBM	B-Device
PC	I-Device
in	O
1980s	O
.	O
</s>
<s>
The	O
ES	B-Device
PEVM	I-Device
models	O
lineup	O
also	O
included	O
analogues	O
of	O
IBM	B-Device
PC	I-Device
XT	O
,	O
IBM	B-Device
PC	I-Device
AT	O
,	O
IBM	O
XT/370	O
.	O
</s>
<s>
The	O
first	O
models	O
of	O
ES	B-Device
PEVM	I-Device
(	O
ES-1840	O
,	O
ES-1841	O
,	O
ES-1842	O
)	O
,	O
unlike	O
the	O
IBM	B-Device
PC	I-Device
,	O
had	O
two	O
units	O
:	O
a	O
system	O
unit	O
and	O
a	O
floppy	O
drives	O
unit	O
.	O
</s>
<s>
These	O
models	O
used	O
a	O
backplane	B-Architecture
instead	O
of	O
the	O
main	O
board	O
.	O
</s>
<s>
Although	O
the	O
system	O
bus	O
was	O
compatible	O
with	O
ISA	B-Architecture
bus	I-Architecture
,	O
it	O
used	O
a	O
different	O
type	O
of	O
connector	O
,	O
so	O
the	O
IBM	B-Device
PC	I-Device
expansion	O
cards	O
could	O
not	O
be	O
installed	O
in	O
ES	B-Device
PEVM	I-Device
.	O
</s>
<s>
were	O
fully	O
compatible	O
with	O
IBM	B-Device
PC	I-Device
XT	O
and	O
IBM	B-Device
PC	I-Device
AT	O
.	O
</s>
<s>
Unlike	O
IBM	B-Device
PC	I-Device
using	O
the	O
Intel	B-Device
8088	I-Device
processor	O
,	O
the	O
early	O
ES	B-Device
PEVM	I-Device
models	O
used	O
K1810VM86	B-Device
processor	O
with	O
a	O
16-bit	O
bus	O
and	O
a	O
clock	O
frequency	O
of	O
5	O
MHz	O
.	O
</s>
<s>
Early	O
versions	O
of	O
the	O
board	O
did	O
not	O
have	O
a	O
socket	O
for	O
the	O
floating	B-Algorithm
point	I-Algorithm
coprocessor	B-General_Concept
.	O
</s>
<s>
CPU	B-Device
board	O
(	O
containing	O
54	O
chips	O
)	O
.	O
</s>
<s>
It	O
was	O
installed	O
in	O
early	O
models	O
of	O
ES	B-Device
PEVM	I-Device
.	O
</s>
<s>
MDA	B-Device
adapter	O
board	O
(	O
containing	O
91	O
chips	O
)	O
.	O
</s>
<s>
It	O
was	O
built	O
using	O
the	O
Bulgarian	O
CM607	O
chip	O
(	O
MC6845	B-General_Concept
clone	B-General_Concept
)	O
.	O
</s>
<s>
CGA	B-Device
adapter	O
board	O
(	O
containing	O
94	O
chips	O
)	O
.	O
</s>
<s>
It	O
was	O
built	O
using	O
the	O
Bulgarian	O
CM609	O
chip	O
(	O
Intel	O
8272	O
clone	B-General_Concept
)	O
.	O
</s>
<s>
It	O
was	O
electrically	O
incompatible	O
with	O
the	O
IBM	B-Device
PC	I-Device
COM	B-Architecture
port	I-Architecture
and	O
was	O
not	O
supported	O
in	O
the	O
BIOS	B-Operating_System
.	O
</s>
<s>
The	O
computers	O
were	O
shipped	O
with	O
AlphaDOS	O
,	O
an	O
entirely	O
Russified	O
version	O
of	O
MS-DOS/PC	O
DOS	O
2.x	O
and	O
3.x	O
.	O
</s>
<s>
All	O
commands	B-Application
were	O
entered	O
in	O
Russian	O
,	O
for	O
example	O
,	O
СМЕНКАТ	O
for	O
CHDIR	B-Application
.	O
</s>
<s>
Early	O
models	O
of	O
ES	B-Device
PEVM	I-Device
were	O
prone	O
to	O
failures	O
due	O
to	O
manufacturing	O
defects	O
.	O
</s>
