By Philippe Dubois, President. Translation by Sébastien Marty.

In this second article, we are going to take a first general tour of the machine to check first of all its overall condition and then start to identify the numerous electronic boards that make it up and see what functions they perform.

The Micral N unit acquired and restored by the MO5 association

The Micral N arrived at the MO5 association’s premises and our best experts are now hard at work studying it. We will first inspect it from every angle, to check that there are no points of corrosion or broken elements. Then, we will begin analysing the electronic boards it contains.

Close-up of the front panel and logo of MO5’s Micral N unit

In accordance to what we observed when we purchased it (see previous article), the machine is visibly in good aesthetic condition. The front panel seems particularly well preserved: there are no broken or missing switches, inscriptions such as the R2E logo, the name of the machine and instructions above each control switch are all present and show no scratches.

Back view of the Micral N showing all the electronic boards that make it run

Turning the machine around, we can see the large set of electronic boards it contains. When we acquired it, we had no idea, nor the seller for that matter, of the function of each board. This is important because the order in which they are plugged in can have an impact on the operation of the computer.

Close-up of some of MO5’s Micral N electronic boards

One of the distinctive features of this historical microcomputer is to use what is called in computer jargon a “backplane”, i.e. a data bus with slots that allow the addition of up to 22 electronic boards, all communicating together.

This is how the Micral N works: there are several input/output boards enabling communication with the outside world, as well as several memory boards (including RAM and ROM with a fixed program) and finally a CPU board that dialogues with all these other boards so that the computer can operate.

Deep inside the computer, the PLURIBUS data bus, patented by R2E

Our unit clearly contains several RAM boards, one or two ROM boards, a CPU board and several input/output boards which we have not identified yet.

We’ll be able now to closely study each of these boards. But that’s a story for a future article, so see you soon!

Meanwhile, remember to take part in the campaign to support our work! https://micral.mo5.com