Over on YouTube [CuriousMarc] and [TubeTimeUS] team up for a multi-part series E&L MMD-1 Mini-Micro Designer Restoration.
The E&L MMD-1 is a microcomputer trainer and breadboard for the Intel 8080. It’s the first ever single-board computer. What’s more, they mention in the video that E&L actually invented the breadboard with the middle trench for the ICs which is so familiar to us today; their US patent 228,136 was issued in August 1973.
The MMD-1 trainer has support circuits providing control logic, clock, bus drivers, voltage regulator, memory decoder, memory, I/O decoder, keyboard encoder, three 8-bit ports, an octal keyboard, and other support interconnects. They discuss in the video the Intel 1702 which is widely accepted as the first commercially available EPROM, dating back to 1971.
In the first video they repair the trainer then enter a “chasing lights” assembly language program for testing and demonstration purposes. This program was found in 8080 Microcomputer Experiments by Howard Boyet on page 76. Another book mentioned is The Bugbook VI by David Larsen et al.
In the second video they wire in some Hewlett-Packard HP 5082-7300 displays which they use to report on values in memory.
A third episode is promised, so stay tuned for that! If you’re interested in the 8080 you might like to read about its history or even how to implement one in an FPGA!
Part 3 came out earlier today: https://www.youtube.com/watch?v=KVV-ybhIXwU
Part 4 is out now too: https://www.youtube.com/watch?v=RTmwdS3TE2Q
I love these old micro trainers, I wish I’d managed to save a few from the dumpster at my local tech college when they decided electronics was no longer a necessary course to offer.
I was able to get two MCS-85 from somewhere.
My first processor was a 8085 at school and the second the TMS9900 in the TI 99/4a.
“and the second the TMS9900 in the TI 99/4a.”
I love the old TI CPUs. Somewhere around here I still have a couple in white ceramic with gold pins. Beautiful.
They came out of some TI-990 minicomputers that I supported a few decades back. Those were beer-fridge-sized machines with dual 8-inch floppies and a genuine “das blinkenlights” panel on the front.
I’m dating myself, but I used the MMD1 for my first microprocessor course. I was already familiar with hex entry using a Heathkit ET3400, and the octal displays and entry drove me crazy. Was very happy when we used the MMD2 in the next course which had hex IO.
I assembled one from a kit back in the 70s ! However I remember mine having a different keyboard and I thought mine had 7 seg display above it. I don’t remember if it was an MMD-1 or 2. Did some coding lessons on it and used the breadboard for powering and setting up some basic gates I bought at Radio Shack.
I remember learning on the MMD-1 when I was at DeVry in Chicago back in the early ’80s. In my last year, they started replacing them with a much smaller 8085 system. Those were the days!
I designed the MMD-1, which my brother Chris and I named the “Dynamicro.” E&L Instruments thought people might mispronounce that name as Dynamic Ro, so it became the Mini Micro Designer. We had designed a larger Micro Designer previously for E&L, but its market was small and limited to schools and universities. The MMD-1 appealed to a wider market. We used octal for all our 8008, 8080, 8085, and Z80 work. We had experience with octal from our times working with DEC PDP-8/L minicomputers that uses octal. The PDP-8’s had 12 bits, so octal was a natural numbering method. It was so easy to learn–no alpha characters to memorize. The original Intel manuals for the 8008 had instructions in decimal–really.
Chris wrote the MMD-1 code, which he called KEX, for Keypad Executive. The keypad circuit used two priority encoders. Chris found an unused pin on one encoder IC and used it as a serial input to load code into MMD-1s we had for students in classes we taught. Students could use an editor-assembler (which Chris also wrote) and quickly download their code serially to an MMD-1.
E&L might have some sort of design patent on a solderless breadboard, but AP Products in Ohio(?) created the first solderless breadboard in 1970 or 1971. It was much better than those from other suppliers because its plastic did not warp. The latter models from E&L and others warped badly. The AP breadboards also had gold-plated contacts. I bought mine in early ’71 for $20. It’s still in my home lab, probably with a Raspberry Pi PICO on it. –Jon Titus
Jon, thanks for tge wonderful design. Your interview is currently scheduled to cap off the series – should be episode 7 at the rate things are going…
Marc
The first single board computer should be cited as the Intel SIM8 (1972). The one that followed shortly after SIM8 was the MYCRO-1 (1974) or the Intel SDK-80 or Motorola MEK6800D1 (both 1975).The Dyna-micro (1976), was rebranded as the MMD-1 in the fall of 1976 and i can see why you declare that as the first commercial SBC. The KIM one, the MOS Technology KIM-1 (1976), was a cheaper and very popular single-board computer based on the MOS 6502 microprocessor. I purchased serial 245 of the AIM65 at full kit price of $999 (which I still have) in fall of 1978 (2nd Yr eTech College). I built up my own local cassette i/o and regularly participated at the OCClub. My school mate had the MM1 8080.
The 8080 is the ancient descendant of the 8086 and we all know what a sucess that started from 1983 and on. I did my eTechnologist thesis on 80286 application while working full time at BellCanada in 1983, and the AssemblyLang will stay with me until I die.
The MM1 was the study basis for course work in 1978 and the basis for many early developmental
Projects.
When I think back that I requisitioned a 10 Megabyte Winchester in 1984 for $1300 I reflect on how far forward we are now.
Calling it the “first single-board computer” may be a bit of a stretch, but it might be the first single board “trainer” type of computer.