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!
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.