<s>
The	O
KC	B-Device
85	I-Device
( 	O
 '	O
KC	O
 '	O
meaning	O
"	O
Kleincomputer	O
"	O
,	O
or	O
"	O
small	O
computer	O
"	O
)	O
were	O
models	O
of	O
microcomputers	B-Architecture
(	O
KC	O
85/2	O
,	O
KC	O
85/3	O
and	O
KC	O
85/4	O
)	O
built	O
in	O
East	O
Germany	O
by	O
VEB	O
Mikroelektronik	O
"	O
Wilhelm	O
Pieck	O
"	O
Mühlhausen	O
.	O
</s>
<s>
The	O
first	O
model	O
in	O
the	O
series	O
,	O
the	O
HC	B-Device
900	I-Device
,	O
originally	O
designed	O
as	O
a	O
home	O
computer	O
and	O
introduced	O
in	O
1984	O
,	O
was	O
renamed	O
to	O
KC	O
85/2	O
in	O
1985	O
to	O
de-empathize	O
its	O
use	O
as	O
consumer	O
good	O
.	O
</s>
<s>
Despite	O
similar	O
names	O
,	O
the	O
KC	B-Device
85	I-Device
computers	O
were	O
not	O
directly	O
related	O
to	O
the	O
KC	B-Device
87	I-Device
series	O
produced	O
by	O
VEB	O
Robotron-Meßelektronik	O
"	O
Otto	O
Schön	O
"	O
Dresden	O
.	O
</s>
<s>
The	O
availability	O
of	O
the	O
KC	B-Device
85	I-Device
series	O
for	O
private	O
customers	O
was	O
very	O
limited	O
.	O
</s>
<s>
They	O
were	O
based	O
on	O
the	O
U880	B-Device
CPU	B-General_Concept
(	O
an	O
East	O
German	O
clone	O
of	O
the	O
Z80	B-General_Concept
)	O
,	O
with	O
clock	O
speeds	O
of	O
1.75MHz	O
(	O
KC	O
85/2	O
,	O
KC	O
85/3	O
)	O
and	O
1.77MHz	O
(	O
KC	O
85/4	O
)	O
.	O
</s>
<s>
Unlike	O
the	O
Pravetz	B-Device
series	I-Device
8	I-Device
personal	O
computers	O
,	O
manufactured	O
in	O
Bulgaria	O
,	O
which	O
were	O
equipped	O
with	O
dedicated	O
displays	O
,	O
floppy	B-Device
disks	I-Device
and	O
quality	O
keyboards	O
,	O
the	O
entire	O
KC	O
series	O
used	O
TV	O
sets	O
for	O
display	O
purposes	O
.	O
</s>
<s>
The	O
KC	B-Device
85	I-Device
used	O
a	O
separate	O
keyboard	O
driven	O
by	O
a	O
remote	O
control	O
IC	O
.	O
</s>
<s>
The	O
KC	O
85/2	O
was	O
the	O
first	O
computer	O
made	O
in	O
Mühlhausen	O
and	O
had	O
only	O
font	O
ROMs	O
for	O
capital	O
letters	O
,	O
and	O
no	O
BASIC	O
in	O
ROM	B-Device
.	O
</s>
<s>
Later	O
,	O
the	O
KC	O
85/3	O
was	O
introduced	O
and	O
this	O
one	O
had	O
a	O
KC-BASIC	O
 [ de ] 	O
interpreter	O
in	O
ROM	B-Device
,	O
freeing	O
the	O
user	O
from	O
having	O
to	O
load	O
it	O
from	O
a	O
cassette	O
every	O
time	O
.	O
</s>
<s>
In	O
fact	O
,	O
the	O
KC	O
85/2	O
and	O
KC	O
85/3	O
were	O
practically	O
indistinguishable	O
in	O
board	O
design	O
except	O
for	O
a	O
different	O
ROM	B-Device
and	O
an	O
internal	O
piezo	O
speaker	O
.	O
</s>
<s>
On	O
the	O
KC85/4	O
the	O
video	O
ram	O
layout	O
was	O
changed	O
in	O
a	O
backwards-incompatible	O
manner	O
to	O
40	O
columns	O
of	O
256	O
bytes	O
and	O
the	O
bytes	O
in	O
one	O
column	O
were	O
put	O
into	O
consecutive	O
memory	O
addresses	O
.	O
</s>
<s>
This	O
limitation	O
was	O
brought	O
down	O
to	O
1×8	O
on	O
the	O
KC	O
85/4	O
(	O
the	O
color	O
cells	O
on	O
both	O
the	O
KC85/3	O
and	O
KC85/4	O
were	O
thus	O
quite	O
small	O
compared	O
to	O
contemporary	O
systems	O
)	O
.	O
</s>
<s>
The	O
KC85/4	O
also	O
featured	O
a	O
special	O
4-color	O
(	O
black	O
,	O
white	O
,	O
red	O
,	O
cyan	O
)	O
mode	O
which	O
could	O
color	O
every	O
pixel	O
independently	O
.	O
</s>
<s>
There	O
was	O
no	O
"	O
text	O
mode	O
"	O
,	O
everything	O
had	O
to	O
be	O
painted	O
;	O
this	O
combined	O
with	O
the	O
video	O
RAM	O
layout	O
described	O
above	O
and	O
ROM	B-Device
code	O
made	O
the	O
KC	O
85/2	O
-3	O
rather	O
slow	O
at	O
printing	O
and	O
scrolling	O
(	O
improved	O
very	O
much	O
on	O
KC	O
85/4	O
)	O
.	O
</s>
<s>
There	O
were	O
no	O
blitters	B-General_Concept
,	O
sprites	O
or	O
hardware	O
scrolling	O
,	O
not	O
a	O
single	O
hardware	O
register	O
with	O
which	O
to	O
influence	O
the	O
display	O
drawing	O
process	O
,	O
the	O
sole	O
exception	O
being	O
the	O
blink	O
attribute	O
,	O
whose	O
frequency	O
could	O
be	O
tuned	O
by	O
programming	O
the	O
dedicated	O
CTC	O
register	O
and	O
which	O
required	O
no	O
CPU	B-General_Concept
assistance	O
.	O
</s>
<s>
The	O
KC85/4	O
added	O
one	O
bit	O
to	O
select	O
which	O
of	O
the	O
two	O
buffers	O
to	O
display	O
and	O
one	O
bit	O
to	O
switch	O
between	O
high	O
color	O
(	O
using	O
color	O
cells	O
)	O
and	O
high	O
color-resolution	O
mode	O
(	O
using	O
the	O
color	O
RAM	O
as	O
a	O
second	O
bit	O
plane	O
)	O
.	O
</s>
<s>
With	O
the	O
KC	O
85/2	O
and	O
KC	O
85/3	O
CPU	B-General_Concept
access	O
to	O
video	O
memory	O
would	O
interfere	O
with	O
screen	O
redraw	O
and	O
cause	O
visual	O
distortions	O
as	O
pixel	O
data	O
could	O
not	O
be	O
read	O
from	O
VRAM	O
and	O
the	O
previously	O
loaded	O
strip	O
of	O
8	O
pixels	O
was	O
simply	O
drawn	O
again	O
.	O
</s>
<s>
This	O
issue	O
was	O
fixed	O
in	O
the	O
KC	O
85/4	O
too	O
-	O
one	O
video	O
period	O
of	O
8	O
horizontal	O
pixels	O
is	O
divided	O
evenly	O
into	O
3	O
phases	O
:	O
(	O
1	O
)	O
an	O
8	O
bit	O
wide	O
CPU	B-General_Concept
access	O
(	O
r/w	O
)	O
,	O
(	O
2	O
)	O
fetch	O
8	O
bits	O
of	O
pixel	O
data	O
and	O
(	O
3	O
)	O
fetch	O
8	O
bits	O
of	O
color	O
data	O
.	O
</s>
<s>
entry	O
point	O
address	O
and	O
so	O
forth	B-Application
.	O
</s>
<s>
The	O
main	O
CPU	B-General_Concept
would	O
thus	O
be	O
interrupted	O
7	O
times	O
for	O
each	O
keystroke	O
and	O
could	O
measure	O
the	O
time	O
between	O
the	O
interrupts	O
to	O
recover	O
the	O
serial	O
data	O
word	O
.	O
</s>
<s>
There	O
was	O
a	O
single	O
8867kHz	O
crystal	O
oscillating	O
at	O
twice	O
the	O
PAL	B-Language
chrominance	O
frequency	O
and	O
a	O
divide-by-10	O
,	O
multiply-by-16	O
phase	O
locked	O
loop	O
was	O
used	O
to	O
derive	O
a	O
14.2MHz	O
clock	O
from	O
which	O
the	O
pixel	O
clock	O
(	O
7.1MHz	O
)	O
and	O
processor	O
clock	O
(	O
1.77MHz	O
)	O
was	O
derived	O
by	O
division	O
by	O
2	O
and	O
8	O
,	O
respectively	O
(	O
KC85/2	O
,	O
KC85/3	O
and	O
KC85/4	O
used	O
the	O
same	O
circuit	O
for	O
this	O
purpose	O
,	O
since	O
the	O
digital	O
to	O
analog	O
video	O
conversion	O
PCB	O
where	O
the	O
clock	O
generation	O
was	O
situated	O
did	O
not	O
change	O
between	O
revisions	O
)	O
.	O
</s>
<s>
There	O
was	O
still	O
a	O
slight	O
difference	O
in	O
effective	O
clock	O
rate	O
,	O
the	O
KC85/2	O
and	O
KC85/3	O
skipped	O
a	O
few	O
CPU	B-General_Concept
cycles	O
at	O
the	O
end	O
of	O
each	O
scanline	O
,	O
to	O
provide	O
in	O
a	O
simple	O
manner	O
to	O
the	O
entire	O
system	O
the	O
illusion	O
of	O
a	O
horizontal	O
resolution	O
(	O
including	O
blanking	O
)	O
divisible	O
by	O
8	O
,	O
the	O
KC85/4	O
did	O
not	O
.	O
</s>
<s>
None	O
of	O
the	O
revisions	O
had	O
provisions	O
for	O
either	O
vertical	O
blank	O
interrupts	O
or	O
horizontal	B-General_Concept
blank	I-General_Concept
interrupts	I-General_Concept
.	O
</s>
<s>
The	O
KC	B-Device
85	I-Device
could	O
be	O
programmed	O
in	O
assembly	B-Language
language	I-Language
and	O
BASIC	O
(	O
the	O
KC	O
85/2	O
had	O
to	O
load	O
BASIC	O
from	O
tape	O
)	O
,	O
but	O
it	O
was	O
possible	O
to	O
use	O
various	O
modules	O
(	O
sold	O
by	O
VEB	O
Mikroelektronik	O
Mühlhausen	O
)	O
or	O
load	O
software	O
from	O
tape	O
,	O
thus	O
allowing	O
programming	O
in	O
Forth	B-Application
and	O
Pascal	B-Application
.	O
</s>
<s>
It	O
was	O
a	O
simple	O
monitor	O
where	O
one	O
could	O
run	O
different	O
"	O
system	O
services	O
"	O
like	O
LOAD	O
(	O
load	O
a	O
program	O
)	O
,	O
JUMP	O
(	O
into	O
extension	O
module	O
ROM	B-Device
)	O
,	O
MODIFY	O
(	O
memory	O
cells	O
)	O
or	O
BASIC	O
(	O
if	O
it	O
had	O
been	O
built	O
into	O
the	O
ROM	B-Device
or	O
had	O
been	O
loaded	O
from	O
tape	O
)	O
.	O
</s>
<s>
In	O
the	O
last	O
years	O
of	O
the	O
GDR	O
,	O
a	O
floppy	B-Device
attachment	O
(	O
"	O
tower	O
"	O
-style	O
,	O
too	O
)	O
was	O
produced	O
.	O
</s>
<s>
It	O
featured	O
a	O
4MHz	O
CPU	B-General_Concept
and	O
a	O
5¼	O
"	O
Floppy	B-Device
drive	I-Device
(	O
you	O
could	O
have	O
up	O
to	O
four	O
of	O
them	O
)	O
.	O
</s>
<s>
These	O
(	O
literally	O
:	O
the	O
U	O
880	O
A	O
in	O
the	O
attachment	O
did	O
)	O
were	O
able	O
to	O
run	O
CP/M	B-Application
,	O
which	O
was	O
called	O
MicroDOS	B-Operating_System
.	O
</s>
<s>
(	O
One	O
had	O
to	O
JUMP	O
from	O
the	O
base	O
system	O
to	O
the	O
floppy	B-Device
system	O
and	O
boot	O
from	O
a	O
floppy	B-Device
—	O
another	O
CAOS	O
or	O
MicroDOS	B-Operating_System
)	O
.	O
</s>
<s>
There	O
were	O
a	O
lot	O
of	O
different	O
projects	O
for	O
the	O
KC	B-Device
85	I-Device
:	O
</s>
