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Disk Drives

I am no longer active in this hobby for the foreseeable future. 
I will no longer maintain or update the website, but I will leave it accessible to the web for as long as possible (years).


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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 entry (entries).

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 even 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 programming.

Diskmon was a fairly reliable and capable program that brought DG computers out of the hobby era and into the modern world!

My Disk System

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.

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Digital Group 8" disk drive system -- Unrestored, unworking

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Cover off, showing dust and grime, missing and loose hardware

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Floppy Disk Interface Card

Although I do have an operational disk system as part of my Mini Bytemaster, it uses the smaller 5-1/4 inch disks. It will be a happy day when I have this piece fully restored and operating. I have a few other projects in line ahead of this, but it won't be long now!!

This system is in pretty rough shape cosmetically and fair shape mechanically. It looks to me as if the mechanical engineering at DG was done by fifth graders! Sure, the cabinets were beautiful, but the mounting of heavy hardware like these drives or the power supplies in the main system just all look like an afterthought at best. The cabinet has sustained damage from loose drives knocking around under their own weight, and all of the structural parts are thin aluminum straps. There will be many hours of work to bring this back to original condition... Oh well, it's DISK!!


I have docs for these on my Digital Group Documentation page.

And now, the pics...

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Dirt and dust at the power switch

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More dirt on the fan

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Better view of the dust :)

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Power supply with no OVP - a DG weak spot

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Shugart drive - a swap meet acquisition

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Shugart drive - soft underbelly

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Cabinet damage to be fixed

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More damage in need of restoration

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Copyright 2008 Bryan's Old Computers
Last modified:
October 16, 2009