Now you can have all your
Nuts & Volts issues from
calendar year 2004 archived
on a CD that can be
searched, printed, and easily
stored.
You can purchase said CD
from us, for your own
personal use, and donate
your old paper copies to
your local school or library.
(Your spouse will love you
for it!)
Earlier years are in the works
as well, so stay tuned for
their availability.
Makes a great gift too.
The holidays are just
around the corner!
F
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NUTS & VOLTS
E
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50
scraps scattered all over the disk, the
Compucolor simply moved up all the
newer files on the disk to fill the gap.
If you didn’t mind the wear and tear
on the disk, this was actually quite a
good solution; there was never any
file fragmentation on a Compucolor.
Of course, this approach meant
copying files, or sections of them, into
the computer’s memory while moving
them. To avoid interfering with programs in RAM, the Compucolor was
smart enough to use the 4K video RAM
as a file buffer. Deleting a file became
something of a visual delight. For
seconds at a time, as disk blocks were
copied first to the screen RAM then
back to the disk, large portions of the
display were taken over by constantly
changing random graphics characters.
FLAKY DISKS
One side effect of the file copying
process was that it graphically
illustrated, quite literally, just how
recalcitrant disk operation could be.
A line of graphics would flicker for
several seconds while the software
read and reread a disk block until it
got a version that agreed with the
check-sum on the disk. That block
would then be written and the nail-biting process would recommence with
another block further down the file.
Unreadable disk blocks were such
a fact of life that I wrote a little Basic
and machine-language program that
let me read a specific block, edit out
errors, and rewrite it to the disk. This
would usually restore an unreadable
file. A popular after-market product
was a mu-metal screen that could isolate the disk drive from the nearby
scan coils of the CRT. I drilled a hole in
the side of the computer’s plastic
case, which let me adjust the drive’s
rotation speed on the fly and get the
best results from a reluctant disk.
When I found that I was replacing
line-scan transistors on a regular basis,
I made another modification: a fan
bolted above the power supply. I’ve not
risked powering up my Compucolor in
its original form since I stopped using
it. On the rare occasions when I use it
to read old files, I connect the motherboard and disk drive to an old
Commodore power supply and a
Commodore RGB-input monitor.
SOFTWARE
When I bought my Compucolor, a
decent range of software was
already available, including a text editor, an 8080 assembler, and a number of games. I bought the chess program. Ultimately, I got it to run 40%
faster by modifying its internal board
representation. When programs were
8K long, one could do things like that.
Imagine modifying one of today’s
humongous game programs to suit
yourself!
I used both the text editor and the
assembler extensively. I eventually
modified the editor to display upper
and lower case characters as different
colored upper-case characters on-screen. When I coupled up a dot
matrix printer, I got normal upper- and
lower-case text. I eventually substituted
a daisy-wheel printer and added features such as micro-justification to the
editor. My text has never looked better.
THE MARKET HAS
ITS WAY
As I’ve indicated, the Compucolor
had its limitations, largely resulting
from its relatively low cost. By 1979,
the 8080 was passé, and those still
using it wanted to run CP/M. Despite
its features and technical ingenuity,
the Compucolor II never became a big
seller. Presumably, potential users
balked at having to come up with the
price of a complete system before
they could get started. There was
an active user group that had a
newsletter, Colorcue, to which I used
to contribute, but no mass following.
Then, in 1981, the FCC introduced new regulations governing the
permissible level of RF radiation
emitted by home computers. A TV
set in a plastic case was governed by
one set of rules. Call it a computer,
though, and a different set of rules
applied. It was no longer possible to
get away with an unshielded case and
ribbon cables carrying high-speed
signals. Updating the Compucolor
wouldn’t have been worth the cost.
FCC regulations or not, I got
good service from my Compucolor II
for another six years. It is a fine example of a technological achievement
that failed in the marketplace. NV
SEPTEMBER 2005
