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It was all polling, no hardware interrupts.
I built a DG computer from kits the company supplied. I figured there were about 14,000 hand soldered joints in the finished product. I did some trouble shooting with a simple pen style logic probe, and found a small defect in a printed PC board that kept a “555″ timer chip from oscillating. After I repaired the board, everything started working.
It took me almost 2 weeks to figure out that in the documentation meant to push the enter key. There was no person I knew (at that time) with computer experience, so I was on my own. The audio cassette tapes worked fine for loading software, but my 4 deck Phi-Deck box never did work, even after much fiddling. The heads would load, the motors would run, but I never got a reliable data transfer. No access to a oscilloscope back then, and to expensive to buy one. I wire-wrapped a board so I could switch from the audio cassette ROM to the Phi-Deck ROM by flipping a toggle switch. I would say I learned a great deal, but never got any really good use from that PC. Mostly I played lunar lander and chess with it. I think I had about $2000 (“real” 1975 dollars) invested in the Digital Group setup. I think it still works about the same as when I built it, except the foam pads in the DG keyboard are shot. I got an E-mail from a guy who replaced the foam on his keyboard, so I guess it can be done if enough time is available. I thought DG was the LEAST likely company to fail, since it seemed the most flexible. I was certainly wrong, but DG did supply everything I paid for in total while slipping into bankruptcy.
I replaced it with an Ampro “Little-Board” single board computer running CP/M 2.2 on 5 1/4 inch floppies. I put the Ampro PC into the cubical case that the Digital Group monochrome monitor came in, along with a power supply, and a “BG Micro” terminal board, that emulated a Lear-Sigler, Heath-Zenith, or DEC terminal. Worked great, and still does to this day, using the “T-Maker” integrated office software package, in 48 kilobytes of RAM.
Too bad about DG, but I probably made back many times the $2000, because I was the only person who knew anything about microprocessors when they started showing up where I worked.
How do you register with this group?
I have 2 big brown boxes with motherboard and power supply as well as a DG keyboard. I have not turned them on in years. I started with a minimum system while I worked for HP in Orlando. When I moved to AL in 77 I got a system for a local accountant and wrote the software he needed for his business. I hated to see the DG go away.
Thanks for starting this site.
I built a DG system in 1978 — for a while I was the only kid in our high school with a computer. Added phidecks after about a year of fun with audio cassettes. I learned a LOT from it (got CP/M running on it, using an Atari 800 floppy disk drive for storage, and got it hooked up to the Arpanet using a terminal emulator I wrote).
I think it would still work, if I replaced the foam on the keyboard. I doubt there are any 300 baud BBS systems to dial into any more, though, much less an Arpanet TAC
Does anyone know where any info is available on AEON boards made for DG computers? I have a system with a Z80B processor on a daughter board that I think is an AEON board.
Previous comment is incorrect. The board turned out to be a R W Sales processor board with a sasi interface on the daughter board. I actually found my old documentation for it although the print quality is poor. I wonder if the sasi interface works directly with a shugart drive. I also found OASIS docs.
If I remember correctly that daughter board connected to a hard drive interface which in turn could connect to an ST-506 type hard drive. Rex (the “R W” part of R W Sales stands for Rex Widmer) eventually made new/updated versions of most of the DG boards including the motherboard and also created new boards which had no DG equivalent.
The January 2013 issue of “QST” magazine has an article abour Dr. Bob Suding, W0LMD, that includes a mention of Digital Group computers. Check it out.
Wow. Seeing “Read Z-80 INITIALIZE Cassette” on my computer screen and the numbers zip across the screen really brings back memories. This was my first computer (I was 11 years old). A few years later we donated the computer to my junior high school where I actually taught their first computer class.
Anyone know where I can get a hold of the original full BASIC (not Mini-BASIC) interpreter for this?
How do you start the emulator in 64-column mode? 64 column BASIC looks odd running in 32 col mode.
Does anyone have a copy of MAXI-BASIC in bin format that would work with the emulator?
I have two systems one that I built in 77. and one I ordered to resale as a dealer in 78. It is a kit still. ( boards and cabinet ) I am still A DEALER but Apple only. The oldest dealer in Tennessee. I have couple of boards made by others. Didn’t get everything I ordered and paid for, but Dr. Suding and team gave me a direction in my career as a microcomputer and I wild ride from Hobby to Mainstream. I still have dealership and are semi-retired with daughter running operations.
I bought a DG machine in 1977. I still have it. My goal is to power it up. I understand that the keyboard needs to be rebuilt and that I should use a varistor to slowly in crease the input voltages to the power supply and hope the capacitors do not burn up. When I get ready to start this process can I get some help from you?
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