The MIL Mod-8

by admin · October 15, 2023

Just recently, I was contacted by Lytle Johnson about a Microsystems International Limited, more commonly referred to as MIL, Mod-8 computer. I was thrilled to learn that he had one and even though I offered him some money for it, he insisted that he give it to me. He was downsizing and wanted to

MIL MOD8 – in Lytle’s wood base

make sure it went to someone who would appreciate it. Well, I believe I am the right person as I have a particular passion for Canadian computers and even though I have pictures on my website of another beautiful MIL Mod-8/80 that features a lot of chips that MIL produced, that one is not mine.

Thanks to Lytle, this one is and I very much appreciate it. I have some pictures below. This one did not come with the original power supply that Lytle used and it did not come with the TV Typewriter he built from Radio-Electronics plans, but he did send me the documentation he received when he ordered it from the Radio-Electronics article. It’s too bad he still did not have his TV Typewriter as well.

The MIL MOD8 computer was designed in 1974 around the MIL MF8008 chip; a second sourced 8008 CPU from Intel. The backplane holds a number of cards that make up the bulk of the computer. The backplane also had an EPROM programmer but this particular build does not have it. Each of the cards have a purpose. Below are pictures that identify what they were used for. This computer came out in the era when the Mark-8 and Scelbi 8H 8008-based computers were on the market. Being one of the first computers to utilize the first 8-bit CPU, it’s design is more primitive than even slightly later computers like the MITS Altair 8800 or IMSAI 8080 but that’s the way they were.

Here are the pictures of the MIL Mod-8. I am still unsure if I will just get it working as is or possibly build up the motherboard (Mod 8-8 board) to add the chip programmer circuitry as is commonly seen when you see pictures of it. This particular model has an Intel 8008 CPU (there was a later upgrade option that allowed for an Intel 8080) and also has an after-market Celetron CMod8-9 card that I will investigate further.

Thanks again Lytle.

MIL MOD8 – side view

Pictures of the motherboard. Notice the slots have indications of what card should go in each of the slots. As note, the unbuilt area on the left is where the EPROM programmer circuitry is normally populated. The bottom cable goes to a RESET switch. The top cable goes to the power supply. The white connector is for the TV Typewriter that uses a 20mA current loop interface.