http://www.thedigitalgroup.org/dg dedicated to the preservation and development of digital group computers Sun, 20 Nov 2011 21:57:09 +0000 hourly 1 http://wordpress.org/?v=3.1.3 http://www.thedigitalgroup.org/dg/?page_id=11#comment-30 James Whitmore Sun, 20 Nov 2011 21:57:09 +0000 http://www.thedigitalgroup.org/dg/?page_id=11#comment-30 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. Regards, Jim Whitmore 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.
Regards,
Jim Whitmore

]]> http://www.thedigitalgroup.org/dg/?page_id=11#comment-23 Chris Mallam Sun, 30 Oct 2011 22:39:24 +0000 http://www.thedigitalgroup.org/dg/?page_id=11#comment-23 It was all polling, no hardware interrupts. It was all polling, no hardware interrupts.

]]> http://www.thedigitalgroup.org/dg/?p=1#comment-1 Mr WordPress Sat, 18 Jun 2011 00:03:56 +0000 http://www.thedigitalgroup.org/dg/?p=1#comment-1 Hi, this is a comment.<br />To delete a comment, just log in and view the post's comments. There you will have the option to edit or delete them. Hi, this is a comment.
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