This post is part of the series on Learning the Data General Nova with simh.
Once upon a time, I worked in a small computer lab attached to an Exxon Nuclear research facility. There were two 16-bit minicomputers: a Modcomp II that my boss and I programmed, and a Data General Nova that another small team programmed. The computers were hooked up to a laser lab where humongous no-kidding burn-holes-in-things lasers were being used to refine uranium. I can’t tell you how powerful the lasers were, because that was (probably still is) classified, but I’ve forgotten anyhow. State secrets are safe with someone whose memory is as bad as mine.
The Modcomp II minicomputer that I programmed was hooked up to sensors that the computer used to collect data during the experiments, storing the data to disk files. My boss wrote the software that collected the data, and I wrote the FORTRAN IV programs that charted the data. We had this fancy Techtronics graphing terminal that my code would draw on, and then a thermal printer that could produce a monochome picture of what was on the screen. After an experiment, I ran my program, took screen prints of the graphs, made copies, and carried the results around to the scientists and engineers. It was fun work, and it was satisfying to have an important part to play.
The Modcomp II was just used for data acquisition–it had no way to influence the world. The Data General Nova was (I believe–this was a while ago) used for real-time control of certain parts of the experiment. Like the Modcomp II, it was hooked up to various sensors, but it also had outputs that it could use to drive things. If I remembered what it could control, I probably couldn’t say, but again, I’ve forgotten so those secrets are safe.
I enjoyed programming that Modcomp. By today’s standards, it was minimal (64K x 16-bits of RAM), but the processor was pretty fast and it had a lot of I/O bandwidth. The instruction set was friendly to write assembly language in, and the OS and compilers were capable. But what it wasn’t was sexy. It came in two 19-inch rack-mount cabinets, full of huge wire-wrapped planes covered with ICs on one side and a dense mat of wires on the other. The OS was reminiscent of mainframes of old. There’s just nothing exciting about that.
The Data General Nova was, in my mind, sexier than the Modcomp II. Its panel looked more modern to me. It was soldered instead of wire-wrapped, which seemed better (it was more reliable, anyhow). Its OS had a more modern feel to it, more like those of the microcomputers that were bursting on the scene. I remember looking over at the guys programming it and feeling a little bit jealous. Even though I enjoyed the Modcomp, the Nova looked like more fun. It might have been a case of “the grass is greener” syndrome.
I never did get a chance to program that Nova, but it turns out that the simh project can simulate it, and they have a licensed copy of the RDOS operating system. Finally, I get a chance to play with the Nova and learn what it’s about. In future blog entries, I will write about my discoveries as I explore the simulated Data General Nova. In the next blog entry, I’ll show how to get simh simulating the Nova even if you know nothing about either. It’ll be a sort of simh/nova “hello world.”