<s>
The	O
Dick	O
Smith	O
Super-80	O
was	O
a	O
Zilog	B-General_Concept
Z80	I-General_Concept
based	O
kit	O
computer	O
developed	O
as	O
a	O
joint	O
venture	O
between	O
Electronics	O
Australia	O
magazine	O
and	O
Dick	O
Smith	O
Electronics	O
.	O
</s>
<s>
Electronics	O
Australia	O
had	O
published	O
a	O
number	O
of	O
computer	O
projects	O
before	O
the	O
Super-80	O
,	O
including	O
the	O
EDUC-8	B-Device
in	O
1974	O
,	O
the	O
Mini	O
Scamp	O
and	O
the	O
DREAM	O
6800	O
Video	O
Computer	O
.	O
</s>
<s>
For	O
this	O
,	O
the	O
purchaser	O
received	O
the	O
computer	O
PCB	O
,	O
an	O
assembly	O
manual	O
(	O
a	O
copy	O
of	O
the	O
construction	O
articles	O
from	O
Electronics	O
Australia	O
)	O
and	O
basic	O
components	O
,	O
including	O
16kB	O
of	O
RAM	B-Architecture
and	O
a	O
2kB	O
EPROM	B-General_Concept
containing	O
a	O
machine	B-General_Concept
code	I-General_Concept
monitor	I-General_Concept
program	O
.	O
</s>
<s>
The	O
Super-80	O
was	O
based	O
on	O
the	O
Zilog	B-General_Concept
Z80	I-General_Concept
8-bit	O
microprocessor	B-Architecture
.	O
</s>
<s>
As	O
standard	O
,	O
it	O
had	O
16kB	O
of	O
dynamic	O
RAM	B-Architecture
in	O
the	O
form	O
of	O
eight	O
4116	O
RAM	B-Architecture
chips	I-Architecture
.	O
</s>
<s>
RAM	B-Architecture
could	O
be	O
expanded	O
to	O
32kB	O
or	O
48kB	O
through	O
the	O
addition	O
of	O
rows	O
of	O
eight	O
4116	O
RAM	B-Architecture
chips	I-Architecture
.	O
</s>
<s>
Instead	O
of	O
an	O
expensive	O
video	O
display	O
controller	O
chip	O
with	O
dedicated	O
memory	O
,	O
the	O
Super-80	O
used	O
discrete	O
TTL	O
logic	O
to	O
implement	O
the	O
video	O
display	O
and	O
512	O
bytes	O
of	O
system	O
RAM	B-Architecture
was	O
shared	O
between	O
the	O
video	O
display	O
and	O
the	O
CPU	O
.	O
</s>
<s>
Fifty	O
times	O
per	O
second	O
,	O
the	O
CPU	O
was	O
turned	O
off	O
for	O
around	O
10ms	O
by	O
asserting	O
the	O
Z80	B-General_Concept
BUSREQ	O
(	O
DMA	B-General_Concept
)	O
pin	O
.	O
</s>
<s>
The	O
video	O
display	O
circuitry	O
would	O
then	O
read	O
from	O
the	O
shared	O
RAM	B-Architecture
while	O
it	O
refreshed	O
the	O
image	O
on	O
the	O
screen	O
.	O
</s>
<s>
The	O
location	O
of	O
the	O
512	O
bytes	O
of	O
video	O
memory	O
was	O
normally	O
at	O
the	O
top	O
of	O
the	O
available	O
RAM	B-Architecture
,	O
but	O
could	O
be	O
changed	O
by	O
writing	O
to	O
an	O
I/O	O
port	O
.	O
</s>
<s>
The	O
keyboard	O
was	O
wired	O
as	O
an	O
8	O
×	O
8	O
matrix	O
and	O
connected	O
to	O
the	O
computer	O
via	O
the	O
two	O
8-bit	O
ports	O
of	O
a	O
Z80	B-General_Concept
PIO	O
chip	O
.	O
</s>
<s>
Pressing	O
the	O
keys	O
<CTRL>, <C> and <4>	O
at	O
the	O
same	O
time	O
generated	O
an	O
interrupt	B-Application
that	O
would	O
perform	O
a	O
"	O
warm	O
start	O
"	O
of	O
the	O
monitor	O
program	O
.	O
</s>
<s>
The	O
keyboard	O
'	O
read	O
 '	O
routine	O
supplied	O
in	O
ROM	B-Device
was	O
"	O
negative	O
edge	O
triggered	O
"	O
and	O
would	O
block	O
while	O
a	O
key	O
was	O
down	O
.	O
</s>
<s>
The	O
standard	O
computer	O
had	O
no	O
serial	O
or	O
parallel	O
I/O	O
as	O
such	O
,	O
relying	O
on	O
the	O
optional	O
S-100	B-Architecture
bus	I-Architecture
interface	O
for	O
I/O	O
and	O
expansion	O
.	O
</s>
<s>
The	O
Z80	B-General_Concept
interrupt	B-Application
line	I-Application
was	O
connected	O
to	O
the	O
keyboard	O
PIO	O
and	O
the	O
"	O
Non	B-General_Concept
Maskable	I-General_Concept
Interrupt	I-General_Concept
"	O
line	O
was	O
not	O
connected	O
.	O
</s>
<s>
The	O
Super-80	O
came	O
with	O
a	O
2kB	O
machine	B-General_Concept
code	I-General_Concept
monitor	I-General_Concept
program	O
in	O
ROM	B-Device
.	O
</s>
<s>
A	O
BASIC	O
interpreter	O
could	O
be	O
purchased	O
either	O
on	O
cassette	O
tape	O
or	O
on	O
a	O
set	O
of	O
three	O
4kB	O
EPROMs	B-General_Concept
.	O
</s>
<s>
The	O
first	O
4kB	O
BASIC	O
EPROM	B-General_Concept
replaced	O
the	O
2kB	O
monitor	O
EPROM	B-General_Concept
supplied	O
with	O
the	O
computer	O
and	O
contained	O
the	O
first	O
2kB	O
of	O
BASIC	O
,	O
plus	O
the	O
monitor	O
program	O
.	O
</s>
<s>
The	O
BASIC	O
interpreter	O
was	O
based	O
on	O
Tiny	B-Language
BASIC	I-Language
rewritten	O
and	O
modified	O
by	O
Ron	O
Harris	O
.	O
</s>
<s>
The	O
Printer	O
Interface	O
was	O
an	O
S-100	B-Architecture
Bus	I-Architecture
card	O
giving	O
the	O
Super-80	O
a	O
Centronics	O
parallel	O
printer	O
port	O
.	O
</s>
<s>
It	O
was	O
based	O
on	O
a	O
6845	B-General_Concept
CRTC	I-General_Concept
I.C.	O
</s>
<s>
and	O
had	O
its	O
own	O
2kB	O
of	O
video	O
RAM	B-Architecture
and	O
2kB	O
of	O
character	O
generator	O
RAM	B-Architecture
.	O
</s>
<s>
Removal	O
of	O
the	O
original	O
DMA	B-General_Concept
based	O
video	O
display	O
effectively	O
doubled	O
the	O
performance	O
of	O
the	O
computer	O
,	O
since	O
the	O
CPU	O
was	O
no	O
longer	O
being	O
disabled	O
50	O
times	O
per	O
second	O
for	O
video	O
display	O
refreshes	O
.	O
</s>
<s>
The	O
board	O
gave	O
the	O
Super-80	O
similar	O
video	O
display	O
capabilities	O
to	O
the	O
Applied	O
Technology	O
Microbee	B-Device
computer	O
,	O
released	O
about	O
six	O
months	O
after	O
the	O
Super-80	O
.	O
</s>
<s>
This	O
led	O
to	O
many	O
Microbee	B-Device
games	O
being	O
ported	O
to	O
the	O
VDUEB	O
equipped	O
Super-80	O
.	O
</s>
<s>
The	O
Universal	O
Floppy	B-Device
Disk	I-Device
Controller	I-Device
(	O
UFDC	O
)	O
was	O
an	O
add-on	O
floppy	B-Device
disk	I-Device
interface	O
developed	O
by	O
Microcomputer	O
Engineering	O
(	O
MCE	O
)	O
.	O
</s>
<s>
The	O
UFDC	O
was	O
based	O
on	O
the	O
Western	O
Digital	O
WD2793	O
floppy	B-Device
disk	I-Device
controller	I-Device
chip	O
and	O
had	O
a	O
Z80	B-General_Concept
DMA	B-General_Concept
controller	I-General_Concept
on	O
board	O
.	O
</s>
<s>
The	O
most	O
popular	O
disk	B-Device
format	I-Device
was	O
5	O
"	O
(	O
133mm	O
)	O
80	O
track	O
,	O
double	O
sided	O
,	O
double	O
density	O
using	O
a	O
Mitsubishi	O
floppy	B-Device
drive	I-Device
mechanism	O
.	O
</s>
<s>
The	O
UFDC	O
's	O
use	O
of	O
DMA	B-General_Concept
required	O
the	O
VDUEB	O
upgrade	O
to	O
be	O
present	O
.	O
</s>
<s>
To	O
install	O
the	O
disk	O
controller	O
,	O
the	O
Z80	B-General_Concept
CPU	O
was	O
removed	O
from	O
the	O
main	O
computer	O
board	O
and	O
installed	O
on	O
the	O
UFDC	O
board	O
.	O
</s>
<s>
This	O
meant	O
that	O
in	O
theory	O
,	O
the	O
UFDC	O
could	O
be	O
used	O
with	O
almost	O
any	O
Z80	B-General_Concept
based	O
system	O
,	O
provided	O
there	O
was	O
enough	O
physical	O
space	O
above	O
the	O
CPU	O
.	O
</s>
<s>
The	O
UFDC	O
used	O
a	O
primitive	O
track	O
based	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
called	O
"	O
Super-80	O
DOS	O
"	O
,	O
however	O
a	O
CP/M	B-Application
BIOS	O
later	O
became	O
available	O
.	O
</s>
<s>
The	O
MXB-1	O
contained	O
space	O
for	O
extra	O
EPROMs	B-General_Concept
,	O
an	O
optional	O
battery	O
backed	O
real	O
time	O
clock	O
,	O
a	O
centronics	O
compatible	O
printer	O
interface	O
and	O
address	O
decoding	O
for	O
up	O
to	O
192kB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
The	O
extra	O
RAM	B-Architecture
was	O
installed	O
by	O
replacing	O
the	O
standard	O
4116	O
16k	O
×	O
1	O
bit	O
RAM	B-Architecture
chips	I-Architecture
with	O
4164	O
64k	O
×	O
1	O
bit	O
RAM	B-Architecture
chips	I-Architecture
.	O
</s>
<s>
The	O
CPU	O
's	O
64kB	O
address	O
limit	O
was	O
worked	O
around	O
through	O
bank	B-General_Concept
switching	I-General_Concept
.	O
</s>
<s>
The	O
MXB-1	O
was	O
mostly	O
of	O
benefit	O
to	O
users	O
running	O
the	O
CP/M	B-Application
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
,	O
since	O
CP/M	B-Application
could	O
then	O
have	O
a	O
full	O
64kB	O
of	O
RAM	B-Architecture
for	O
programs	O
,	O
with	O
up	O
to	O
128kB	O
being	O
used	O
as	O
a	O
small	O
RAM	B-Application
disk	I-Application
.	O
</s>
<s>
The	O
El	O
Graphix	O
"	O
X-RAM	O
"	O
board	O
provided	O
up	O
to	O
16K	O
of	O
battery	O
backed	O
CMOS	O
RAM	B-Architecture
or	O
EPROM	B-General_Concept
.	O
</s>
<s>
Several	O
X-RAM	O
boards	O
could	O
be	O
piggybacked	O
allowing	O
each	O
to	O
be	O
port	O
selected	O
as	O
independent	O
16K	O
banks	O
of	O
memory	O
.	O
</s>
<s>
This	O
memory	O
took	O
the	O
form	O
of	O
8	O
x	O
2K	O
24pin	O
sockets	O
which	O
accepted	O
either	O
2016	O
CMOS	O
RAM	B-Architecture
or	O
2716	O
EPROMS	B-General_Concept
.	O
</s>
<s>
As	O
the	O
system	O
ROM	B-Device
shared	O
part	O
of	O
the	O
address	O
range	O
taken	O
up	O
by	O
the	O
X-RAM	O
board	O
the	O
system	O
ROM	B-Device
could	O
be	O
copied	O
into	O
CMOS	O
RAM	B-Architecture
on	O
the	O
fly	O
and	O
modified	O
as	O
required	O
to	O
actively	O
add	O
or	O
modify	O
custom	O
functions	O
into	O
the	O
operating	O
system	O
.	O
</s>
