the software on a system whose three
plug-in memory cards stored a total
of 12 KB and had cost my employers
In 1979, I finally bought a computer of my own. Right from the start,
I’d decided to buy the best home computer available and to stick with it.
That’s why I picked the Compucolor II.
It left all its contemporaries in the
dust, yet today, virtually no one has
ever heard of it. I was still using mine
in 1987, when I bowed to the inevitable
and bought an Amiga 500. In 1992, I
upgraded to the Amiga 3000 I still use.
As I said, I stick with the best.
BOTTOM UP OR
Early home computers were designed
from the ground up. Developers
introduced new features as fast as they
could design them, and customers
gobbled them up. You started with a
minimal, barely usable machine with
integer Basic and scarcely enough
memory to run it. You fought the family for use of the TV as a display device
and you struggled to get programs to
store and load on an audiocassette
recorder. Eventually, you’d expand the
RAM capacity, buy a floating point
Basic, or even add a disk drive. The TV
remained the only display option.
Dedicated computer monitors were
rare, hugely expensive, and monochrome. Besides, the RF output from
your computer wouldn’t drive one.
The Compucolor II bucked this
trend. For a start, it was designed not
by a bunch of enthusiasts working on
a shoestring, but by an offshoot of the
Intelligent Systems Corp., a commercial computer and monitor company.
Rather than adding on to a minimal
system, its designers scaled down a
professional product. By the standards
of the day, its floating-point, graphics-capable Basic was a marvel and its
development was already paid for.
The Compucolor’s plastic case
had been designed for a 13” portable
TV (see Photo 1). Where you’d expect
to find the TV’s tuner, there was a 5-
1/4” floppy disk drive. Down the other
side of the CRT was the chassis that
held the power supply and the line
and frame scan circuitry. Under the
tube, you’d find the computer board
with an 8080 processor and from 8K
to 32K of RAM. Its 16K of ROM held
the disk operating system and Basic.
RAM could be extended to 40K
with an add-on board. The advantage
to an add-on was that neither Basic
nor the operating system was aware of
its existence. It was the perfect place
to run your own assembly language
programs without fear that they might
be overwritten. Photo 2 shows the
motherboard with two add-on memory
boards — one static and one dynamic.
At a time when most home
computers had rubber membrane
keyboards that were cumbersome and
inconvenient, the Compucolor had a
real keyboard with real keys. It was a
standard Intecolor part, a solidly built
unit linked to the computer with a ribbon cable about four feet long. You no
longer needed to perch the TV on top of
the computer and sit with your nose a
foot from the screen. Basic keywords
could be entered with single keystrokes.
128 x 128 resolution. The built-in
Basic had a full set of point-and-line
All of the pixels in a block shared
the same color. If you wanted control
over the colors of individual picture
elements, you had to settle for 64x64
blocks of four pixels each.
AND A DISK DRIVE,
A REAL DISPLAY
Apart from being the only home
computer of its generation whose
disk drive wasn’t an optional extra, the
Compucolor’s distinction was its built-in display tube with direct RGB drive.
Not only did you have higher resolution than computers driving TV sets,
but you also had eight colors and full
saturation, rather than the limited
range of pastel shades that the Apple
II could manage. I used to show mine
off at computer clubs; its dazzling
color display blew people away.
The character generator limited
you to upper-case-only, but you
could display 64 characters
on each of 32 lines.
could only manage 40 characters
by 24 lines. Each
character had an
attribute byte that let
you choose any two of
the eight colors for a character’s background and
foreground. You soon learned
which combinations were readable and which ones were not.
Because any character
could be replaced by a 2x4 pixel
block, you could plot graphs with
The Compucolor’s 5-1/4” disk drive
was completely non-standard. It read
and wrote data using a TMS5501
timer/port/UART chip in its high-speed
test mode. Each disk stored 51,200
bytes as 400 blocks of 128 bytes —
probably the lowest disk capacity of
any commercially available computer.
You doubled it by flipping your disks
over and putting another 400 blocks on
the back. This procedure worked most
of the time, even though disk-drive
experts condemned it.
The disk operating system was a
masterpiece of simplicity. Each disk
had a number of blocks allocated to
its directory, as selected by the user;
each block addressed six files. Each
file occupied a contiguous area of the
disk. If you edited and saved a file, it
was automatically assigned a new
version number and appended to the
disk and the directory.
The fun started when you deleted
an unwanted file. Unlike the modern
approach of marking disk blocks as
deleted and writing
new files in
PHOTO 2. A fully-loaded
Much of the control logic was
implemented in 16-pin PROM chips.