<s>
The	O
Compukit	B-Device
UK101	I-Device
microcomputer	B-Architecture
(	O
1979	O
)	O
is	O
a	O
kit	O
clone	B-General_Concept
of	O
the	O
Ohio	B-Application
Scientific	I-Application
Superboard	B-Application
II	I-Application
single-board	B-Device
computer	I-Device
,	O
with	O
a	O
few	O
enhancements	O
for	O
the	O
UK	O
market	O
-	O
notably	O
replacing	O
the	O
24×24	O
(	O
add	O
guardband	O
kit	O
to	O
give	O
32×32	O
)	O
screen	O
display	O
with	O
a	O
more	O
useful	O
48×16	O
layout	O
working	O
at	O
UK	O
video	O
frequencies	O
.	O
</s>
<s>
The	O
video	O
output	O
is	O
black	O
and	O
white	O
with	O
256	O
semigraphic	B-Data_Structure
characters	O
generated	O
by	O
a	O
two	O
kilobyte	O
ROM	B-Device
.	O
</s>
<s>
The	O
UK101	B-Device
design	O
was	O
published	O
in	O
Practical	O
Electronics	O
,	O
a	O
popular	O
hobbyists	O
magazine	O
at	O
the	O
time	O
.	O
</s>
<s>
Kits	O
of	O
parts	O
for	O
building	O
the	O
machine	O
were	O
available	O
from	O
Compukit	B-Device
Ltd	O
.	O
/	O
CompShop	O
Ltd	O
.	O
of	O
14	O
Station	O
Road	O
,	O
Barnet	O
,	O
Hertfordshire	O
.	O
</s>
<s>
The	O
Compukit	B-Device
UK101	I-Device
is	O
powered	O
by	O
a	O
6502	B-General_Concept
microprocessor	I-General_Concept
CPU	O
running	O
at	O
1MHz	O
,	O
and	O
is	O
equipped	O
with	O
up	O
to	O
8	O
kilobytes	O
of	O
RAM	B-Architecture
using	O
2114	O
static	B-Architecture
RAM	I-Architecture
chips	O
of	O
1024×	O
4-bit	O
.	O
</s>
<s>
An	O
additional	O
memory-mapped	B-Architecture
1	O
KB	O
of	O
RAM	B-Architecture
is	O
used	O
for	O
the	O
video	O
display	O
.	O
</s>
<s>
It	O
has	O
the	O
8K	B-Language
Microsoft	I-Language
BASIC	I-Language
interpreter	O
stored	O
in	O
ROM	B-Device
.	O
</s>
<s>
In	O
addition	O
to	O
Basic	O
,	O
a	O
6502	B-General_Concept
machine	B-General_Concept
code	I-General_Concept
monitor	I-General_Concept
(	O
2K	O
bytes	O
)	O
is	O
built	O
into	O
ROM	B-Device
.	O
</s>
<s>
It	O
allows	O
programming	O
by	O
entering	O
sequences	O
of	O
6502	B-General_Concept
opcodes	B-Language
.	O
</s>
<s>
Later	O
a	O
two-pass	O
assembler	B-Language
was	O
available	O
which	O
allows	O
the	O
use	O
of	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
Although	O
the	O
6502	B-General_Concept
has	O
two	O
interrupt	O
input	O
pins	O
(	O
NMI	O
and	O
IRQ	O
)	O
,	O
neither	O
is	O
used	O
by	O
the	O
UK101	B-Device
.	O
</s>
<s>
The	O
UK101	B-Device
has	O
a	O
16-row	O
,	O
48-column	O
memory-mapped	B-Architecture
character	O
semigraphics	B-Data_Structure
display	O
,	O
with	O
each	O
character	O
taking	O
up	O
8x8	O
pixels	O
with	O
an	O
aspect	O
ratio	O
of	O
about	O
1:2	O
(	O
corresponding	O
to	O
an	O
effective	O
resolution	O
of	O
384x128	O
)	O
.	O
</s>
<s>
The	O
keyboard	O
of	O
the	O
UK101	B-Device
is	O
located	O
on	O
the	O
main	O
PCB	O
,	O
and	O
comprises	O
a	O
matrix	O
of	O
keyswitches	O
.	O
</s>
<s>
The	O
matrix	O
is	O
interfaced	O
to	O
the	O
CPU	O
via	O
two	O
8-bit	O
I/O	B-Architecture
ports	I-Architecture
,	O
and	O
is	O
polled	O
by	O
firmware	O
in	O
the	O
machine	O
's	O
ROMs	O
.	O
</s>
<s>
Because	O
the	O
keyboard	O
lacks	O
any	O
way	O
to	O
generate	O
an	O
interrupt	O
,	O
it	O
is	O
not	O
possible	O
to	O
implement	O
a	O
typeahead	B-Device
buffer	I-Device
.	O
</s>
<s>
The	O
UK101	B-Device
uses	O
the	O
Kansas	B-Device
City	I-Device
standard	I-Device
tape	O
format	O
.	O
</s>
<s>
I/O	O
is	O
managed	O
by	O
a	O
Motorola	O
6850	O
ACIA	B-Architecture
.	O
</s>
<s>
Although	O
very	O
similar	O
to	O
the	O
Ohio	B-Application
Scientific	I-Application
Superboard	B-Application
II	I-Application
,	O
the	O
Compukit	B-Device
UK101	I-Device
differed	O
from	O
that	O
machine	O
in	O
a	O
few	O
places	O
:	O
</s>
<s>
Video	O
display	O
of	O
the	O
UK101	B-Device
works	O
at	O
UK	O
frequency	O
and	O
resolution	O
.	O
</s>
<s>
However	O
,	O
similarities	O
in	O
the	O
PCB	O
layout	O
make	O
it	O
clear	O
that	O
this	O
machine	O
is	O
a	O
clone	B-General_Concept
.	O
</s>
<s>
The	O
people	O
involved	O
with	O
the	O
modifications	O
were	O
Chris	B-Application
Cary	I-Application
and	O
Bill	O
Wood	O
.	O
</s>
<s>
The	O
40	O
pin	O
expansion	O
socket	O
opened	O
up	O
the	O
world	O
to	O
the	O
UK101	B-Device
.	O
</s>
<s>
One	O
could	O
attach	O
a	O
dual	O
floppy	B-Device
disk	I-Device
controller	O
(	O
5.25	B-Device
"	I-Device
)	O
and	O
a	O
memory	O
expansion	O
card	O
(	O
40K	O
max	O
)	O
to	O
allow	O
faster	O
and	O
reliable	O
save/load	O
of	O
programs/data	O
.	O
</s>
<s>
A	O
sound	O
card	O
became	O
available	O
,	O
built	O
around	O
the	O
General	B-Device
Instrument	I-Device
AY-3-8910	I-Device
,	O
which	O
together	O
with	O
a	O
Peripheral	O
Interface	O
Adapter	O
(	O
PIA	O
)	O
WDC	B-Application
65C21	I-Application
chip	O
,	O
gave	O
the	O
UK101	B-Device
audio	O
abilities	O
.	O
</s>
<s>
The	O
UK101	B-Device
floppy	B-Device
disk	I-Device
interface	O
utilised	O
a	O
PIA	O
to	O
control	O
the	O
floppy	B-Device
disk	I-Device
drive	I-Device
stepper	O
motor	O
and	O
another	O
ACIA	B-Architecture
to	O
serialise	O
the	O
data	O
written	O
to	O
the	O
disk	O
.	O
</s>
<s>
A	O
disk	O
operating	O
system	O
was	O
used	O
to	O
provide	O
file	O
storage	O
capability	O
but	O
this	O
resided	O
in	O
RAM	B-Architecture
and	O
so	O
reduced	O
the	O
available	O
program	O
space	O
.	O
</s>
<s>
Typically	O
single	O
or	O
double	O
sided	O
40	O
track	O
floppy	B-Device
drives	I-Device
could	O
be	O
supported	O
.	O
</s>
<s>
The	O
power	O
consumption	O
of	O
an	O
expanded	O
UK101	B-Device
could	O
require	O
up	O
to	O
5	O
Amps	O
at	O
5.0Vdc	O
(	O
25	O
Watts	O
)	O
,	O
so	O
heat	O
dissipation	O
and	O
power	O
supply	O
de-coupling	O
were	O
common	O
challenges	O
.	O
</s>
