<s>
The	O
Big	O
Board	O
(	O
1980	O
)	O
and	O
Big	O
Board	O
II	O
(	O
1982	O
)	O
were	O
Z80	B-General_Concept
based	O
single-board	B-Device
computers	I-Device
designed	O
by	O
Jim	O
Ferguson	O
.	O
</s>
<s>
They	O
provided	O
a	O
complete	O
CP/M	B-Application
compatible	O
computer	O
system	O
on	O
a	O
single	O
printed	O
circuit	O
board	O
,	O
including	O
CPU	B-Device
,	O
memory	O
,	O
disk	O
drive	O
interface	O
,	O
keyboard	B-Device
and	O
video	O
monitor	O
interface	O
.	O
</s>
<s>
The	O
printed	O
circuit	O
board	O
was	O
sized	O
to	O
match	O
the	O
Shugart	O
801	O
or	O
851	O
floppy	B-Device
drive	I-Device
.	O
</s>
<s>
This	O
allowed	O
attachment	O
to	O
up	O
to	O
two	O
8inch	O
or	O
5	O
1/4inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
The	O
Big	O
Board	O
II	O
added	O
a	O
SASI	O
interface	O
which	O
could	O
be	O
used	O
to	O
drive	O
hard	B-Device
drives	I-Device
,	O
enhancements	O
to	O
system	O
speed	O
(	O
4MHz	O
vs.	O
2.5MHz	O
)	O
and	O
enhancements	O
to	O
the	O
terminal	O
interface	O
.	O
</s>
<s>
One	O
version	O
of	O
the	O
Big	O
Board	O
was	O
used	O
in	O
the	O
Xerox	B-Device
820	I-Device
.	O
</s>
<s>
In	O
its	O
most	O
popular	O
form	O
,	O
the	O
fully	O
assembled	O
and	O
tested	O
Big	O
Board	O
need	O
only	O
be	O
connected	O
to	O
a	O
power	O
supply	O
,	O
one	O
or	O
two	O
eight	O
inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
a	O
composite	O
monitor	O
,	O
and	O
an	O
ASCII	B-Protocol
encoded	O
keyboard	B-Device
in	O
order	O
to	O
provide	O
a	O
fully	O
functioning	O
system	O
.	O
</s>
<s>
A	O
serial	B-General_Concept
terminal	I-General_Concept
could	O
be	O
used	O
in	O
place	O
of	O
the	O
monitor	O
and	O
keyboard	B-Device
,	O
further	O
simplifying	O
assembly	O
.	O
</s>
<s>
Many	O
different	O
modifications	O
to	O
increase	O
the	O
system	O
clock	O
speed	O
were	O
possible	O
,	O
including	O
some	O
that	O
required	O
nothing	O
more	O
than	O
jumpers	B-Device
(	O
e.g.	O
</s>
<s>
There	O
was	O
also	O
a	O
minor	O
industry	O
in	O
user-installable	O
system	O
upgrades	O
such	O
as	O
real	O
time	O
clocks	O
,	O
4MHz	O
upgrades	O
,	O
double	B-Device
density	I-Device
floppy	B-Device
upgrades	O
,	O
character	O
enhancements	O
for	O
the	O
display	O
(	O
reverse	O
video	O
,	O
blinking	O
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
and	O
the	O
addition	O
of	O
hard	B-Device
disk	I-Device
interfaces	I-Device
such	O
as	O
SASI	O
and	O
SCSI	B-Architecture
.	O
</s>
<s>
While	O
not	O
directly	O
supported	O
by	O
CP/M	B-Application
,	O
the	O
extra	O
memory	O
could	O
be	O
used	O
to	O
implement	O
a	O
ram	B-Application
disk	I-Application
,	O
caching	B-General_Concept
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
image	O
(	O
to	O
greatly	O
improve	O
warm	B-Operating_System
boot	I-Operating_System
time	O
)	O
,	O
or	O
a	O
print	B-Device
spooler	I-Device
.	O
</s>
<s>
The	O
Big	O
Board	O
was	O
designed	O
primarily	O
to	O
run	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
,	O
version	O
2.2	O
.	O
</s>
<s>
It	O
came	O
with	O
a	O
monitor	O
program	O
in	O
ROM	B-Device
called	O
PFM-80	O
which	O
was	O
the	O
"	O
software	O
front	O
panel	O
"	O
of	O
the	O
system	O
.	O
</s>
<s>
The	O
board	O
featured	O
3	O
spare	O
2K	O
ROM	B-Device
sockets	O
that	O
allowed	O
for	O
the	O
addition	O
of	O
additional	O
firmware	B-Application
.	O
</s>
<s>
Popular	O
additions	O
were	O
Tiny	B-Language
BASIC	I-Language
,	O
FORTH	O
,	O
and	O
enhanced	O
versions	O
of	O
PFM	O
.	O
</s>
<s>
The	O
Big	O
Board	O
came	O
with	O
a	O
full	O
set	O
of	O
schematics	B-Application
,	O
a	O
document	O
titled	O
"	O
Theory	O
of	O
Operation	O
"	O
,	O
the	O
PFM-80	O
User	O
's	O
Manual	O
,	O
instructions	O
for	O
assembly	O
and	O
testing	O
of	O
the	O
Big	O
Board	O
,	O
a	O
parts	O
list	O
,	O
and	O
addenda	O
to	O
these	O
.	O
</s>
<s>
The	O
Theory	O
of	O
Operation	O
described	O
the	O
details	O
of	O
the	O
operation	O
of	O
the	O
system	O
,	O
including	O
the	O
CRT	B-General_Concept
controller	I-General_Concept
,	O
floppy	B-Device
disk	I-Device
controller	I-Device
,	O
serial	B-Protocol
communications	I-Protocol
,	O
memory	O
bank	B-General_Concept
switching	I-General_Concept
,	O
and	O
connector	O
pinouts	B-Application
.	O
</s>
<s>
Z80	B-General_Concept
CPU	B-Device
at	O
2.5MHz	O
.	O
</s>
<s>
64	O
KB	O
dynamic	O
RAM	B-Architecture
in	O
32	O
4116s	O
or	O
equivalent	O
.	O
</s>
<s>
An	O
ASCII	B-Protocol
keyboard	B-Device
interface	O
.	O
</s>
<s>
A	O
TTL	B-General_Concept
/	O
composite	O
video	O
CRT	B-Device
interface	O
allowing	O
a	O
display	O
of	O
24	O
lines	O
by	O
80	O
characters	O
.	O
</s>
<s>
A	O
SS/SD	O
floppy	B-Device
disk	I-Device
interface	O
allowing	O
addition	O
of	O
up	O
to	O
four	O
8	B-Device
"	I-Device
Shugart	O
Associates	O
SA800	O
compatible	O
8	B-Device
"	I-Device
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
Z80	B-General_Concept
CPU	B-Device
at	O
4MHz	O
.	O
</s>
<s>
64	O
KB	O
dynamic	O
RAM	B-Architecture
in	O
8	O
4164s	O
or	O
equivalent	O
.	O
</s>
<s>
SASI/SCSI	O
hard	B-Device
disk	I-Device
interface	O
,	O
also	O
usable	O
as	O
a	O
general	O
purpose	O
I/O	O
or	O
for	O
control	O
of	O
other	O
SCSI	B-Architecture
devices	O
.	O
</s>
<s>
An	O
ASCII	B-Protocol
keyboard	B-Device
interface	O
.	O
</s>
<s>
A	O
TTL	B-General_Concept
/	O
composite	O
video	O
CRT	B-Device
interface	O
allowing	O
a	O
display	O
of	O
24	O
lines	O
by	O
80	O
characters	O
.	O
</s>
<s>
A	O
DS/DD	O
floppy	B-Device
disk	I-Device
interface	O
allowing	O
addition	O
of	O
up	O
to	O
four	O
8	B-Device
"	I-Device
or	O
5.25	B-Device
"	I-Device
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
Two	O
RS-232	O
serial	O
ports	O
via	O
a	O
Z80	B-General_Concept
SIO	O
.	O
</s>
<s>
A	O
parallel	O
Centronics	O
compatible	O
printer	O
port	O
via	O
a	O
Z80	B-General_Concept
PIO	O
.	O
</s>
<s>
6	O
ROM/EPROM	O
sockets	O
,	O
including	O
ability	O
to	O
program	O
EPROMs	O
in	O
place	O
.	O
</s>
<s>
The	O
Xerox	B-Device
820	I-Device
computer	O
was	O
based	O
on	O
the	O
Big	O
Board	O
;	O
InfoWorld	O
stated	O
that	O
its	O
"	O
considerable	O
virtues	O
...	O
lie	O
mostly	O
in	O
its	O
use	O
of	O
the	O
Big	O
Board	O
's	O
design	O
"	O
.	O
</s>
<s>
Shugart	O
Associates	O
was	O
a	O
common	O
source	O
of	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
as	O
was	O
Tandon	O
Corporation	O
.	O
</s>
<s>
Taylor	O
Electric	O
Company	O
provided	O
the	O
"	O
Better	O
Board	O
"	O
,	O
including	O
floppy	B-Device
disk	I-Device
drive	I-Device
interface	O
enhancements	O
,	O
enhancements	O
to	O
PFM	O
,	O
and	O
corrections	O
to	O
the	O
original	O
assembly	O
and	O
testing	O
instructions	O
bundled	O
with	O
the	O
Big	O
Board	O
.	O
</s>
<s>
SWP	O
Microcomputer	O
Products	O
of	O
Arlington	O
,	O
TX	O
(	O
formerly	O
Software	O
Publishers	O
)	O
provided	O
the	O
Bigboard	B-Device
Dual	O
Density	O
upgrade	O
,	O
which	O
provided	O
both	O
hardware	O
and	O
software	O
to	O
allow	O
the	O
Big	O
Board	O
I	O
to	O
use	O
dual	O
density	O
formats	O
on	O
its	O
drives	O
.	O
</s>
<s>
Micro	O
Cornucopia	O
provided	O
many	O
products	O
to	O
enhance	O
the	O
Big	O
Board	O
computers	O
,	O
including	O
speed	O
upgrades	O
,	O
utility	O
software	O
and	O
development	O
tools	O
both	O
on	O
ROM	B-Device
and	O
on	O
disk	O
,	O
and	O
I/O	O
enhancements	O
.	O
</s>
<s>
D&W	O
Associates	O
of	O
Rome	O
,	O
NY	O
sold	O
monitors	O
,	O
ASCII-encoded	O
keyboards	B-Device
,	O
and	O
power	O
supplies	O
targeted	O
to	O
the	O
Big	O
Board	O
market	O
.	O
</s>
<s>
Several	O
manufacturers	O
provided	O
real	O
time	O
clock	O
upgrades	O
as	O
a	O
CPU	B-Device
daughter	O
board	O
.	O
</s>
<s>
Andy	O
Bakkers	O
sold	O
a	O
1	O
MB	O
RAM	B-Application
Disk	I-Application
daughter	O
board	O
for	O
Big	O
Board	O
II	O
.	O
</s>
