<s>
The	O
Tangerine	B-Device
Microtan	I-Device
65	I-Device
(	O
sometimes	O
abbreviated	O
M65	O
)	O
was	O
a	O
6502	B-General_Concept
based	O
single	O
board	O
microcomputer	B-Architecture
,	O
first	O
sold	O
in	O
1979	O
,	O
which	O
could	O
be	O
expanded	O
into	O
,	O
what	O
was	O
for	O
its	O
day	O
,	O
a	O
comprehensive	O
and	O
powerful	O
system	O
.	O
</s>
<s>
The	O
design	O
became	O
the	O
basis	O
for	O
what	O
later	O
became	O
the	O
ORIC	B-Device
ATMOS	O
and	O
later	O
computers	O
,	O
which	O
has	O
similar	O
keyboard	B-Device
addressing	O
and	O
tape	O
I/O	B-General_Concept
as	O
in	O
the	O
Microtan	B-Device
65	I-Device
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
has	O
a	O
single	O
step	O
function	O
that	O
can	O
be	O
used	O
for	O
debugging	O
at	O
the	O
hardware	B-Architecture
level	O
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
was	O
intended	O
as	O
a	O
general	O
purpose	O
microcomputer	B-Architecture
which	O
could	O
be	O
used	O
by	O
laboratories	O
,	O
Original	O
Equipment	O
Manufacturers	O
(	O
OEMs	O
)	O
and	O
the	O
computer	O
enthusiast	O
,	O
and	O
it	O
was	O
designed	O
with	O
expandability	O
in	O
mind	O
.	O
</s>
<s>
Price	O
of	O
the	O
Microtan	B-Device
65	I-Device
board	O
in	O
1981	O
was	O
£79.35	O
(	O
inc	O
.	O
VAT	O
)	O
in	O
kit	O
form	O
or	O
£90.85	O
ready-assembled	O
.	O
</s>
<s>
To	O
accompany	O
the	O
hardware	B-Architecture
and	O
to	O
offer	O
further	O
support	O
to	O
users	O
,	O
a	O
magazine	O
was	O
created	O
,	O
the	O
Tansoft	O
Gazette	O
(	O
name	O
inspired	O
by	O
the	O
Liverpool	O
Software	O
Gazette	O
)	O
.	O
</s>
<s>
This	O
was	O
edited	O
by	O
Tangerine	O
employee	O
Paul	O
Kaufman	O
who	O
continued	O
as	O
editor	B-Application
when	O
the	O
magazine	O
was	O
renamed	O
Oric	B-Device
Owner	O
.	O
</s>
<s>
Tansoft	O
also	O
became	O
the	O
name	O
of	O
Tangerine	O
Computer	O
's	O
official	O
software	O
house	O
which	O
supplied	O
a	O
number	O
of	O
software	O
products	O
and	O
books	O
for	O
the	O
Microtan	O
system	O
and	O
subsequently	O
for	O
the	O
Oric	B-Device
range	O
of	O
computers	O
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
was	O
quite	O
simple	O
by	O
today	O
's	O
standards	O
,	O
with	O
:	O
</s>
<s>
The	O
major	O
advance	O
that	O
the	O
Microtan	B-Device
65	I-Device
had	O
over	O
a	O
lot	O
of	O
the	O
competition	O
at	O
that	O
time	O
was	O
that	O
the	O
video	B-Device
display	I-Device
was	O
flicker	O
free	O
.	O
</s>
<s>
At	O
the	O
time	O
a	O
lot	O
of	O
microcomputers	B-Architecture
would	O
either	O
access	O
the	O
screen	O
memory	O
asynchronously	O
to	O
the	O
video	O
timing	O
(	O
causing	O
flicker	O
and	O
splats	O
on	O
the	O
screen	O
)	O
,	O
or	O
would	O
write	O
to	O
the	O
screen	O
memory	O
during	O
a	O
non-display	O
period	O
(	O
which	O
was	O
slow	O
)	O
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
got	O
over	O
this	O
problem	O
by	O
making	O
use	O
of	O
an	O
incidental	O
feature	O
of	O
the	O
6502	B-General_Concept
.	O
</s>
<s>
The	O
6502	B-General_Concept
(	O
unlike	O
most	O
other	O
CPUs	B-Device
)	O
has	O
a	O
regular	O
period	O
in	O
each	O
instruction	O
cycle	O
when	O
all	O
CPU	B-Device
activity	O
is	O
inside	O
the	O
chip	O
,	O
leaving	O
the	O
external	O
memory	O
available	O
without	O
using	O
complex	O
external	O
arbitration	O
logic	O
.	O
</s>
<s>
This	O
made	O
video	B-Device
display	I-Device
design	O
simpler	O
and	O
meant	O
that	O
video	O
accesses	O
could	O
be	O
made	O
at	O
maximum	O
speed	O
.	O
</s>
<s>
This	O
technique	O
is	O
also	O
used	O
on	O
the	O
Oric-1	B-Device
and	O
Atmos	O
,	O
and	O
in	O
the	O
unrelated	O
Apple	B-Device
II	I-Device
.	O
</s>
<s>
The	O
32×16	O
characters	O
was	O
the	O
reason	O
that	O
the	O
6502	B-General_Concept
was	O
clocked	O
at	O
750kHz	O
.	O
</s>
<s>
To	O
get	O
the	O
circuitry	O
to	O
work	O
at	O
a	O
(	O
nearly	O
)	O
standard	O
video	O
rate	O
meant	O
that	O
the	O
pixel	B-Algorithm
clock	O
had	O
to	O
be	O
6	O
MHz	O
.	O
</s>
<s>
When	O
the	O
Microtan	B-Device
65	I-Device
was	O
designed	O
only	O
a	O
1MHz	O
6502	B-General_Concept
was	O
available	O
,	O
and	O
so	O
750kHz	O
was	O
used	O
(	O
6MHz	O
divided	O
by	O
8	O
)	O
.	O
</s>
<s>
The	O
1K	O
byte	O
monitor	B-Application
program	I-Application
(	O
later	O
increased	O
to	O
a	O
2K	O
)	O
is	O
called	O
TANBUG	O
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
memory	O
map	O
is	O
shown	O
below	O
( $	O
representing	O
a	O
hexadecimal	O
memory	O
address	O
)	O
:	O
</s>
<s>
In	O
addition	O
to	O
the	O
standard	O
8	O
bits	O
of	O
screen	O
RAM	B-Architecture
,	O
there	O
was	O
an	O
additional	O
single	O
bit	O
RAM	B-Architecture
shadowing	O
the	O
to	O
space	O
.	O
</s>
<s>
This	O
was	O
configured	O
as	O
a	O
9th	O
bit	O
write-only	O
plane	O
,	O
and	O
was	O
used	O
by	O
the	O
Microtan	B-Device
65	I-Device
for	O
rudimentary	O
,	O
or	O
"	O
chunky	O
"	O
,	O
graphics	O
.	O
</s>
<s>
Setting	O
the	O
9th	O
bit	O
displayed	O
a	O
Minitel	B-Application
type	O
block	O
graphic	O
.	O
</s>
<s>
The	O
character	O
representation	O
is	O
standard	O
ASCII	B-Protocol
.	O
</s>
<s>
Several	O
pieces	O
of	O
Microtan	B-Device
65	I-Device
software	O
write	O
to	O
the	O
bottom	O
line	O
by	O
writing	O
to	O
memory	O
starting	O
at	O
-	O
the	O
leftmost	O
character	O
on	O
the	O
bottom	O
line	O
,	O
rather	O
than	O
vectoring	O
through	O
TANBUG	O
.	O
</s>
<s>
I/O	B-General_Concept
in	O
the	O
Microtan	B-Device
65	I-Device
is	O
decoded	O
into	O
a	O
16	O
KB	O
space	O
to	O
simplify	O
the	O
hardware	B-Architecture
.	O
</s>
<s>
In	O
fact	O
the	O
1	O
KB	O
of	O
RAM	B-Architecture
is	O
mirrored	O
through	O
the	O
bottom	O
32	O
KB	O
,	O
the	O
I/O	B-General_Concept
through	O
the	O
next	O
16	O
KB	O
,	O
and	O
the	O
EPROM	B-General_Concept
through	O
the	O
top	O
16	O
KB	O
.	O
</s>
<s>
In	O
common	O
with	O
other	O
6502	B-General_Concept
designs	O
,	O
I/O	B-General_Concept
is	O
mapped	B-Architecture
into	O
the	O
memory	O
space	O
.	O
</s>
<s>
There	O
is	O
no	O
dedicated	O
I/O	B-General_Concept
space	O
as	O
on	O
the	O
Z80	B-General_Concept
,	O
8086	B-General_Concept
etc	O
.	O
</s>
<s>
The	O
I/O	B-Architecture
ports	I-Architecture
are	O
(	O
when	O
fully	O
decoded	O
)	O
:	O
</s>
<s>
Without	O
a	O
TANEX	O
board	O
,	O
and	O
due	O
to	O
deliberately	O
ambiguous	O
address	O
decoding	O
,	O
the	O
address	O
would	O
appear	O
to	O
the	O
6502	B-General_Concept
to	O
have	O
the	O
same	O
data	O
as	O
.	O
</s>
<s>
In	O
TANBUG	O
,	O
this	O
is	O
a	O
jump	O
to	O
an	O
internal	O
monitor	B-General_Concept
routine	O
.	O
</s>
<s>
XBUG	O
provided	O
features	O
such	O
as	O
cassette	B-Device
tape	I-Device
loading	O
and	O
saving	O
,	O
a	O
simple	O
assembler	O
/	O
disassembler	O
,	O
hex	O
calculator	O
.	O
</s>
<s>
The	O
ROM	B-Device
sockets	O
on	O
TANEX	O
could	O
be	O
used	O
to	O
run	O
a	O
10K	O
Microsoft	B-Language
Extended	I-Language
BASIC	I-Language
,	O
a	O
two-pass	O
assembler	O
,	O
or	O
even	O
(	O
and	O
more	O
likely	O
given	O
the	O
hardware	B-Architecture
bias	O
of	O
the	O
Microtan	B-Device
65	I-Device
)	O
code	O
written	O
for	O
a	O
specific	O
hardware	B-Architecture
control	O
application	O
.	O
</s>
<s>
Price	O
of	O
the	O
TANEX	O
board	O
in	O
1981	O
was	O
as	O
a	O
"	O
minimum	O
configuration	O
"	O
kit	O
-	O
lacking	O
one	O
of	O
the	O
6522	O
VIAs	O
and	O
the	O
6551	O
and	O
with	O
1K	O
of	O
RAM	B-Architecture
-	O
and	O
£60.95	O
for	O
a	O
similar	O
board	O
fully	O
assembled	O
.	O
</s>
<s>
The	O
Microtan	B-Device
65	I-Device
was	O
designed	O
as	O
a	O
modular	O
system	O
able	O
to	O
be	O
expanded	O
as	O
required	O
,	O
and	O
for	O
this	O
each	O
board	O
included	O
an	O
80-pin	O
connector	O
at	O
one	O
end	O
allowing	O
it	O
to	O
be	O
plugged	O
into	O
a	O
backplane-type	O
motherboard	B-Device
.	O
</s>
<s>
A	O
simple	O
two-socket	O
"	O
Mini	O
Motherboard	B-Device
"	O
connected	O
the	O
Microtan	B-Device
65	I-Device
and	O
TANEX	O
boards	O
for	O
minimum	O
expansion	O
and	O
in	O
this	O
form	O
the	O
system	O
was	O
also	O
available	O
ready-built	O
from	O
Tangerine	O
,	O
complete	O
with	O
case	O
and	O
full	O
ASCII	B-Protocol
keyboard	B-Device
,	O
as	O
the	O
Tangerine	O
Micron	O
,	O
costing	O
£395.00	O
in	O
1981	O
.	O
</s>
<s>
For	O
further	O
expansion	O
the	O
builder	O
could	O
purchase	O
the	O
full	O
"	O
System	O
Motherboard	B-Device
"	O
which	O
featured	O
an	O
additional	O
ten	O
sockets	O
,	O
bringing	O
the	O
total	O
available	O
sockets	O
to	O
twelve	O
.	O
</s>
<s>
Additional	O
boards	O
became	O
available	O
with	O
time	O
,	O
including	O
a	O
40K	O
memory	O
board	O
-	O
TANRAM	O
,	O
made	O
up	O
of	O
32K	O
of	O
dynamic	O
and	O
8K	O
of	O
static	B-Architecture
RAM	I-Architecture
,	O
bringing	O
the	O
total	O
non-paged	O
memory	O
to	O
48K	O
,	O
a	O
dedicated	O
parallel	O
I/O	B-General_Concept
board	O
featuring	O
16	O
parallel	O
input/output	B-General_Concept
ports	O
;	O
a	O
similar	O
dedicated	O
serial	O
I/O	B-General_Concept
board	O
featuring	O
8	O
serial	O
input/output	B-General_Concept
ports	O
,	O
a	O
disk	B-General_Concept
controller	I-General_Concept
board	O
for	O
use	O
with	O
disk	B-Device
drives	I-Device
,	O
a	O
Disk	B-Operating_System
Operating	I-Operating_System
System	I-Operating_System
-	O
TANDOS	O
65	O
,	O
a	O
high	O
resolution	O
graphics	O
board	O
featuring	O
8K	O
of	O
static	B-Architecture
graphics	O
RAM	B-Architecture
giving	O
a	O
resolution	O
of	O
256	O
×	O
256	O
pixels	B-Algorithm
,	O
a	O
dedicated	O
32K	O
ROM	B-Device
board	O
,	O
(	O
aimed	O
mainly	O
at	O
OEM	O
and	O
general	O
purpose	O
applications	O
or	O
for	O
use	O
with	O
AIM	B-Device
,	O
KIM	B-Device
and	O
SYM	B-Device
systems	O
)	O
,	O
capable	O
of	O
holding	O
either	O
8	O
×	O
2732	O
or	O
16	O
×	O
2716	O
EPROMs	B-General_Concept
;	O
and	O
a	O
32K	O
RAM	B-Architecture
board	O
featuring	O
two	O
16K	O
banks	O
of	O
4116	O
dynamic	O
RAM	B-Architecture
,	O
again	O
intended	O
for	O
similar	O
purposes	O
to	O
the	O
32K	O
ROM	B-Device
board	O
.	O
</s>
<s>
In	O
addition	O
,	O
several	O
third-party	O
suppliers	O
offered	O
boards	O
designed	O
for	O
use	O
with	O
the	O
Microtan	B-Device
65	I-Device
system	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
BASIC	O
programming	O
language	O
Tangerine	O
also	O
released	O
on	O
disk	O
TANFORTH	O
,	O
an	O
extended	O
version	O
of	O
FIG	B-Application
FORTH	I-Application
featuring	O
a	O
full	O
FORTH	O
compiler	B-Language
and	O
editor	B-Application
.	O
</s>
