<s>
The	O
Research	B-Device
Machines	I-Device
380Z	I-Device
(	O
often	O
called	O
the	O
RML	B-Device
380Z	I-Device
or	O
RM	B-Device
380Z	I-Device
)	O
was	O
an	O
early	O
8-bit	O
microcomputer	B-Architecture
produced	O
by	O
Research	O
Machines	O
in	O
Oxford	O
,	O
England	O
,	O
from	O
1977	O
to	O
1985	O
.	O
</s>
<s>
The	O
380Z	O
used	O
a	O
Z80	B-General_Concept
microprocessor	I-General_Concept
(	O
hence	O
the	O
name	O
)	O
with	O
up	O
to	O
56KB	O
of	O
user	O
RAM	B-Architecture
.	O
</s>
<s>
When	O
fitted	O
with	O
an	O
optional	O
floppy	B-Device
disk	I-Device
drive	I-Device
the	O
system	O
ran	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
The	O
basic	O
system	O
came	O
with	O
a	O
text-only	B-Application
monochrome	O
video	B-Device
card	I-Device
,	O
which	O
could	O
be	O
enhanced	O
with	O
a	O
320×192	O
high-resolution	B-Algorithm
graphics	B-Device
board	I-Device
.	O
</s>
<s>
The	O
380Z	O
was	O
packaged	O
in	O
a	O
large	O
,	O
black	O
,	O
19-inch	O
rack-mount	O
,	O
rectangular	O
metal	O
case	O
containing	O
the	O
power	O
supply	O
,	O
a	O
number	O
of	O
printed	O
circuit	O
boards	O
and	O
the	O
optional	O
5¼-inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
The	O
front	B-Device
panel	I-Device
had	O
a	O
pair	O
of	O
strong	O
carrying	O
handles	O
,	O
a	O
keyswitch	O
and	O
a	O
reset	O
button	O
.	O
</s>
<s>
The	O
keyboard	B-Device
was	O
separate	O
and	O
came	O
in	O
a	O
tough	O
metal	O
case	O
.	O
</s>
<s>
Early	O
versions	O
were	O
contained	O
in	O
a	O
light	O
blue	O
metal	O
case	O
with	O
a	O
white	O
front	O
and	O
had	O
only	O
a	O
cassette	O
interface	O
or	O
8-inch	B-Device
floppy	I-Device
drives	O
;	O
only	O
a	O
small	O
number	O
of	O
these	O
were	O
made	O
.	O
</s>
<s>
An	O
optional	O
8-bit	O
ASCII	B-Protocol
paper	O
tape	O
punch/reader	O
was	O
also	O
used	O
,	O
as	O
this	O
was	O
a	O
common	O
storage	O
medium	O
at	O
the	O
time	O
-	O
where	O
previous	O
use	O
of	O
a	O
computer	O
had	O
been	O
limited	O
to	O
a	O
teletype	O
machine	O
connected	O
to	O
mainframe	B-Architecture
by	O
telephone	O
.	O
</s>
<s>
The	O
system	O
used	O
a	O
passive	O
bus	B-General_Concept
architecture	O
with	O
no	O
motherboard	O
–	O
all	O
electronics	O
were	O
contained	O
on	O
a	O
number	O
of	O
cards	O
interconnected	O
by	O
ribbon	O
cable	O
.	O
</s>
<s>
The	O
only	O
microprocessor	B-Device
offered	O
was	O
a	O
4MHz	O
Z80A	B-General_Concept
.	O
</s>
<s>
Memory	O
was	O
fitted	O
in	O
up	O
to	O
four	O
banks	O
of	O
RAM	B-Architecture
,	O
each	O
of	O
either	O
4KB	O
(	O
4×1024	O
bytes	B-Application
)	O
or	O
16KB	O
,	O
although	O
not	O
every	O
permutation	O
was	O
permitted	O
.	O
</s>
<s>
Main	O
memory	O
was	O
not	O
used	O
by	O
the	O
text	O
or	O
graphics	O
video	B-Device
cards	I-Device
,	O
although	O
memory	O
on	O
the	O
video	B-Device
cards	I-Device
was	O
bank	B-General_Concept
switched	I-General_Concept
into	O
a	O
dedicated	O
1.5KB	O
address	O
block	O
.	O
</s>
<s>
The	O
380Z	O
was	O
also	O
fitted	O
with	O
up	O
to	O
6KB	O
of	O
firmware	B-Application
,	O
known	O
as	O
COS	O
.	O
On	O
systems	O
fitted	O
with	O
less	O
than	O
64KB	O
of	O
RAM	B-Architecture
the	O
COS	O
reserved	O
1KB	O
of	O
system	O
RAM	B-Architecture
,	O
leaving	O
the	O
rest	O
available	O
to	O
the	O
user	O
.	O
</s>
<s>
On	O
the	O
64KB	O
RAM	B-Architecture
system	O
a	O
total	O
of	O
56KB	O
was	O
available	O
to	O
the	O
user	O
,	O
with	O
the	O
remainder	O
used	O
by	O
COS	O
or	O
inaccessible	O
because	O
of	O
the	O
firmware	B-Application
ROM	B-Device
,	O
video	B-Device
card	I-Device
,	O
and	O
memory-mapped	B-Architecture
I/O	I-Architecture
.	O
</s>
<s>
COS	O
3.4	O
(	O
see	O
below	O
)	O
and	O
earlier	O
systems	O
came	O
with	O
a	O
basic	O
video	B-Device
card	I-Device
providing	O
a	O
40×24	O
text-only	B-Application
monochrome	O
display	O
.	O
</s>
<s>
Later	O
systems	O
were	O
supplied	O
with	O
an	O
enhanced	O
video	B-Device
card	I-Device
that	O
was	O
software-switchable	O
between	O
40×24	O
and	O
80×24	O
character	O
modes	O
and	O
supported	O
a	O
number	O
of	O
character	O
attributes	O
(	O
underline	O
,	O
dim	O
,	O
reverse-video	O
)	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
text-mode	B-Application
video	B-Device
card	I-Device
the	O
system	O
could	O
be	O
enhanced	O
with	O
a	O
high-resolution	B-Algorithm
graphics	O
(	O
HRG	O
)	O
board	O
.	O
</s>
<s>
High	B-Algorithm
resolution	I-Algorithm
:	O
320×192	O
pixels	B-Algorithm
,	O
2	O
bits	O
per	O
pixel	B-Algorithm
(	O
4	O
colours	O
)	O
,	O
1	O
page	B-General_Concept
.	O
</s>
<s>
Medium	O
resolution	O
:	O
160×96	O
pixels	B-Algorithm
,	O
4	O
bits	O
per	O
pixel	B-Algorithm
(	O
16	O
colours	O
)	O
,	O
2	O
pages	O
.	O
</s>
<s>
A	O
programmable	O
lookup	B-Data_Structure
table	I-Data_Structure
with	O
an	O
8-bit	O
output	O
mapped	O
the	O
pixel	B-Algorithm
value	O
to	O
one	O
of	O
256	O
different	O
colours	O
(	O
analogue	O
RGB	O
output	O
)	O
or	O
intensities	O
(	O
composite	O
video	O
)	O
.	O
</s>
<s>
This	O
arrangement	O
is	O
known	O
as	O
8-bit	O
color	O
and	O
also	O
used	O
on	O
other	O
machines	O
like	O
the	O
MSX2	B-Operating_System
or	O
Atari	B-Device
Falcon	I-Device
.	O
</s>
<s>
Output	O
from	O
the	O
graphics	B-Device
board	I-Device
was	O
mixed	O
with	O
output	O
from	O
the	O
text-only	B-Application
video	B-Device
card	I-Device
,	O
allowing	O
text	O
and	O
graphics	O
to	O
be	O
easily	O
overlaid	O
.	O
</s>
<s>
Mass	B-Device
storage	I-Device
was	O
either	O
via	O
cassette	B-Device
tape	I-Device
or	O
floppy	B-Device
disk	I-Device
(	O
which	O
required	O
a	O
disk	B-General_Concept
controller	I-General_Concept
card	O
)	O
.	O
</s>
<s>
The	O
cassette	O
interface	O
operated	O
at	O
either	O
300bit/s	O
(	O
CUTS	B-Device
standard	O
)	O
or	O
1200bit/s	O
.	O
</s>
<s>
Early	O
systems	O
could	O
be	O
fitted	O
with	O
an	O
optional	O
single	B-Device
density	I-Device
floppy	B-Device
disk	I-Device
controller	I-Device
card	O
that	O
could	O
interfaced	O
to	O
either	O
internal	O
5¼-inch	O
or	O
external	O
8-inch	B-Device
floppy	I-Device
disk	O
drives	O
.	O
</s>
<s>
Disk	O
capacity	O
was	O
80KB	O
per	O
side	O
on	O
5¼-inch	B-Device
disks	I-Device
and	O
250.25KB	O
per	O
side	O
on	O
8-inch	O
disks	O
.	O
</s>
<s>
CP/M	B-Application
used	O
the	O
first	O
4	O
tracks	O
on	O
5¼-inch	B-Device
disks	I-Device
and	O
the	O
first	O
3	O
tracks	O
on	O
8-inch	O
disks	O
,	O
reducing	O
the	O
usable	O
capacity	O
of	O
a	O
single	B-Device
density	I-Device
,	O
single-sided	O
5¼-inch	B-Device
disk	I-Device
to	O
72KB	O
.	O
</s>
<s>
Later	O
systems	O
(	O
referred	O
to	O
as	O
the	O
380Z-D	O
)	O
were	O
fitted	O
with	O
a	O
double	B-Device
density	I-Device
Intelligent	O
Disc	O
Controller	O
(	O
IDC	O
)	O
,	O
which	O
increased	O
disk	O
capacity	O
to	O
either	O
180KB	O
(	O
48	O
TPI	B-Device
drives	O
)	O
or	O
360KB	O
(	O
96	O
TPI	B-Device
drives	O
)	O
per	O
side	O
on	O
5¼-inch	B-Device
disks	I-Device
and	O
500.5KB	O
per	O
side	O
on	O
8-inch	O
disks	O
.	O
</s>
<s>
Support	O
for	O
a	O
"	O
Winchester	O
"	O
hard	B-Device
disk	I-Device
drive	I-Device
could	O
be	O
provided	O
using	O
an	O
intelligent	O
Host	O
Interface	O
Board	O
(	O
HIB	O
)	O
that	O
implemented	O
a	O
SASI	O
interface	O
.	O
</s>
<s>
Hard	B-Device
disk	I-Device
systems	O
were	O
mainly	O
used	O
as	O
file	B-Application
servers	I-Application
for	O
networked	O
LINK	B-Device
480Z	I-Device
systems	O
.	O
</s>
<s>
The	O
passive	O
bus	B-General_Concept
allowed	O
a	O
number	O
of	O
cards	O
to	O
be	O
installed	O
in	O
the	O
380Z	O
.	O
</s>
<s>
CPU/RAM	O
–	O
holding	O
the	O
Z80A	B-General_Concept
CPU	B-General_Concept
,	O
firmware	B-Application
ROMs	O
,	O
and	O
up	O
to	O
32KB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
The	O
card	O
also	O
provided	O
a	O
parallel	O
Centronics	B-Device
printer	I-Device
port	I-Device
(	O
not	O
always	O
connected	O
)	O
.	O
</s>
<s>
RAM	B-Architecture
–	O
a	O
second	O
CPU/RAM	O
board	O
,	O
with	O
processor	O
and	O
ROMs	O
omitted	O
,	O
holding	O
up	O
to	O
a	O
further	O
32KB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
Floppy	B-Device
Disc	I-Device
Controller	O
(	O
FDC	O
)	O
–	O
a	O
single	B-Device
density	I-Device
disk	I-Device
controller	O
,	O
which	O
also	O
provided	O
an	O
RS-232	O
serial	O
interface	O
(	O
SIO-4	O
)	O
.	O
</s>
<s>
Intelligent	O
Disc	O
Controller	O
(	O
IDC	O
)	O
–	O
a	O
double	B-Device
density	I-Device
disk	B-General_Concept
controller	I-General_Concept
with	O
its	O
own	O
dedicated	O
microprocessor	B-Device
.	O
</s>
<s>
High	B-Algorithm
Resolution	I-Algorithm
Graphics	O
(	O
HRG	O
)	O
–	O
up	O
to	O
320×192	O
pixels	B-Algorithm
.	O
</s>
<s>
Host	O
Interface	O
Board	O
(	O
HIB	O
)	O
–	O
for	O
hard	B-Device
disk	I-Device
support	O
.	O
</s>
<s>
380Z	O
Network	O
Interface	O
Board	O
(	O
380Z-NET	O
)	O
–	O
a	O
proprietary	O
800kbit/s	O
network	O
interface	O
used	O
to	O
interconnect	B-General_Concept
to	O
a	O
network	O
of	O
LINK	O
480Zs	O
.	O
</s>
<s>
PIO	O
Interface	O
Development	O
Board	O
–	O
providing	O
three	O
Z80	B-General_Concept
PIOs	O
and	O
a	O
Z80	B-General_Concept
CTC	O
.	O
</s>
<s>
Analogue	O
I/O	B-General_Concept
Board	O
–	O
providing	O
16	O
input	O
channels	O
and	O
2	O
output	O
channels	O
.	O
</s>
<s>
The	O
system	O
firmware	B-Application
contained	O
only	O
a	O
basic	O
monitor	O
program	O
,	O
known	O
as	O
COS	O
(	O
standing	O
for	O
Cassette	O
Operating	B-General_Concept
System	I-General_Concept
in	O
the	O
COS	O
3.4	O
and	O
earlier	O
systems	O
and	O
Central	O
Operating	B-General_Concept
System	I-General_Concept
in	O
the	O
later	O
disk-only	O
systems	O
)	O
.	O
</s>
<s>
The	O
monitor	O
could	O
be	O
used	O
to	O
load	O
application	O
programs	O
,	O
such	O
as	O
BASIC	O
,	O
from	O
cassette	O
or	O
to	O
boot	B-Operating_System
the	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
.	O
</s>
<s>
COS	O
also	O
provided	O
a	O
software	O
front	B-Device
panel	I-Device
allowing	O
the	O
display	O
of	O
registers	O
and	O
memory	O
,	O
and	O
supporting	O
breakpoints	O
and	O
single-stepping	O
of	O
machine	O
code	O
.	O
</s>
<s>
The	O
COS	O
monitor	O
was	O
stored	O
in	O
either	O
4KB	O
(	O
COS	O
3.4	O
and	O
earlier	O
)	O
or	O
6KB	O
(	O
COS	O
4.0	O
and	O
later	O
)	O
of	O
ROM	B-Device
;	O
in	O
the	O
latter	O
case	O
part	O
of	O
the	O
ROM	B-Device
was	O
bank	B-General_Concept
switched	I-General_Concept
.	O
</s>
<s>
COS	O
provided	O
a	O
number	O
of	O
basic	O
hardware	O
control	O
functions	O
,	O
such	O
as	O
keyboard	B-Device
input	O
,	O
writing	O
text	O
to	O
the	O
video	B-Device
card	I-Device
and	O
disk	O
input/output	B-General_Concept
.	O
</s>
<s>
COS	O
functions	O
were	O
called	O
by	O
means	O
of	O
the	O
Emulator	O
Trap	B-Application
(	O
EMT	O
)	O
pseudo-opcode	O
,	O
which	O
used	O
the	O
Z80	B-General_Concept
RST30H	O
instruction	O
to	O
call	O
the	O
EMT	O
handler	O
function	O
.	O
</s>
<s>
The	O
EMT	O
handler	O
read	O
the	O
first	O
byte	B-Application
following	O
the	O
RST30H	O
instruction	O
to	O
determine	O
which	O
EMT	O
function	O
was	O
being	O
requested	O
;	O
all	O
parameters	O
were	O
passed	O
in	O
registers	O
.	O
</s>
<s>
A	O
call-relative	O
pseudo-opcode	O
was	O
also	O
implemented	O
using	O
RST28H	O
.	O
</s>
<s>
COS	O
2.3	O
–	O
cassette-only	O
,	O
40×24	O
video	B-Device
card	I-Device
.	O
</s>
<s>
COS	O
3.0	O
–	O
floppy	B-Device
disk	I-Device
support	O
.	O
</s>
<s>
COS	O
3.4	O
–	O
main	O
COS	O
version	O
supporting	O
single	B-Device
density	I-Device
disks	I-Device
and	O
the	O
40×24	O
video	B-Device
card	I-Device
.	O
</s>
<s>
COS	O
4.2	O
–	O
double	B-Device
density	I-Device
disk	O
drives	O
(	O
380Z-D	O
)	O
.	O
</s>
<s>
The	O
main	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
was	O
CP/M	B-Application
,	O
initially	O
CP/M	B-Application
1.4	O
and	O
later	O
CP/M	B-Application
2.2	O
.	O
</s>
<s>
MP/M	B-Operating_System
II	O
was	O
used	O
on	O
the	O
file	B-Application
server	I-Application
version	O
,	O
which	O
supported	O
a	O
network	O
of	O
LINK	B-Device
480Z	I-Device
computers	O
using	O
CP/NET	O
.	O
</s>
<s>
Many	O
standard	O
CP/M	B-Application
applications	O
were	O
available	O
,	O
such	O
as	O
WordStar	B-Application
.	O
</s>
<s>
Research	O
Machines	O
also	O
produced	O
their	O
own	O
assembler	B-Language
(	O
ZASM	O
)	O
,	O
text	B-Application
editor	I-Application
(	O
TXED	O
)	O
and	O
BASIC	O
interpreter	B-Application
.	O
</s>
