The Digital Group Disk Drive
Sometime around July of 1977, The Digital Group announced the addition
of disk drives to the already large line of DG products. The official announcement
was made in Flyer #10, and in print ads over the next few months. DG was a
little slow to bring the disk drive to market, possibly due to the
investment in the Phideck concept, which was
a tape based storage system and low cost alternative to disks. But, the
difficult problem of transport alignment in the Phideck system made tape
exchange difficult, and software distribution of tape media
impractical--besides, the world had moved to disks as the software
interchange method of choice. DG had no choice but to go along or be left
behind. They were a little late, but in plenty time to enjoy some good success with their
At the same time this 8" dual
drive system was announced, DG also announced a dual 5-1/4 inch drive
system that looked almost identical, but smaller. Known as the Mini Floppy
system, I have yet to find one, though it is high on my Wish
List. Hint, hint.
Marketing of the disk system
focused on the larger 8" disks, which had become something of a
standard in the micro computing world, rather than the newer 5-1/4 inch
disks. DG used Innovex, Pertec, and
Shugart disk drives with a DG designed interface that supported up to four
drives of the same physical size (no mixing of 8" with 5-1/4"
drives permitted). Formatted capacity of an 8" disk was about 300K
bytes, while the Mini Disks could hold 160K bytes each. Software included
with each system consisted of 'driver' routines to Initialize a disk, Seek
to a track, Read or Write a block or data, as well as several test
routines. These were Spartan times!
Nearly everyone who had ordered the
earlier Phideck system, and who
now saw the disk systems, either ordered one, or wanted one -- I know I
did! Disks were FAST and reliable, and though everything associated with disk systems
were very expensive, the benefits were just so tempting. For a moment, I
considered selling my '66 Ford Mustang to get one, but get this--that
would have still left me short of what a single disk system cost! Can
you imagine? Yeah, those were the days!
Diskmon 1.0, written by David
Bryant, was the Digital Group disk operating system. It was a very simple
program that allowed users to manage their disk system and do some
programming. Diskmon made loading and running programs even easier than it
already was with a DG system, and it was very fast by any standard.
OK, yes, our computers today are millions of times more powerful, but
wouldn't it be cool to turn on your PC and have it ready to go before you
could get your finger off the power switch? :)
Diskmon offered the
following commands: Load, Save, Run, Directory, Copy, Delete, Format,
Rename, as well as commands to Read and Write audio cassettes, and
commands to manage a Phideck system too. There were also a whole range of
commands for modifying the Diskmon operating system to add or modify
commands. Diskmon also allowed users to write their own programs with the
built-in editor, though most programmers would load an assembler to do
Diskmon was a fairly reliable and capable program that
brought DG computers out of the hobby era and into the modern world!
The disk system you see here was offered to me a few
years ago by a non-collector type (Lucky for me! :) who was interested in
reclaiming his garage. As I received it, there was only one drive in the
cabinet, and it was in the same condition you see it here otherwise. This
is a future restoration project.