Documenting the recreation of an IBM 1130 computer

NEWEST POSTS AT END - this blog is sequenced with first post at top. To achieve this, I had to date the posts with false dates, this one at the end of 2013 and the ones below on earlier days. Thus the archive list on the bottom right of the blog will refer to Dec, Nov, Oct and Sep 2013 for the posts. To see more posts, go to bottom of page and click on "Older Posts" but for convenience, a list of the most recent are on the top right of this page. . 

I have very fond memories of the IBM 1130 computer, as it was the first computer that I could spend hours on in the wee hours of the morning, after all the official work it had to process was completed. This helped me really grok the way it worked, stepping through programs and watching how it worked by way of the operator console, lights and switches primarily.

The system was produced in the same era as the IBM 360 series of mainframes, back in the 1960s, primarily using punched cards to submit programs and a high speed printer for the output of your work, but also providing a typewriter and keyboard that was used infrequently for certain programs or tasks.

It would be a blast to own one and toy with it for nostalgia, but impractical in several ways. Very few of these still exist, perhaps less than ten worldwide, and only two or three are even in operating condition. They are power hungry and space wasting - particularly when you add the card reader, keypunch to create the punched cards, line printer and other devices you need for a functional system. In some ways, the devices attached to the computer are as rare in their own light and challenging to acquire. My garage does not have room to host a working 1130 system, nor is it a high priority to spend the substantial amounts likely required to buy and restore the system.

Fortunately, modern technology has advanced incredibly far from the capabilities available decades ago. In a physical IBM 1130, the logic required hundreds of printed circuit boards each with dozens of components, while a single logic chip today can encompass all of the 1130 circuits and much more. Further, the speed of today's technology is so much faster that timing is not a challenge - no matter how complex a set of logical steps might be necessary to recreate the behavior of any circuit in the 1130, those steps can be stuck in the infinitessimal gaps between the glacially slow logic signals of the 1130, given the enormity of the speed advantage available today.

This blog will document my journey from desire to idea to recreated IBM 1130. It will not be a recreation in the sense that a museum would attempt, as that would seek to build a machine that looked almost identical to the real 1130 and used as close to identical parts and materials as is possible. Instead, my aim is to maximize the 1130 "experience", where I would be able to replicate the looks, sounds and behaviors from my youthful 1130 interactions, within some practical bounds.

The irony of that adjective - practical - will be apparent as you follow this journey to the recreation. As time went on, my threshold of practicality moved and moved again, involving more and more detailed recreations of the actual appearance and behavior. Not to spoil the reading of the blog too much, but at some point I decided I could recreate the console typewriter, the light panel, switches, buttons and keyboard. This involves modifying IBM Selectric typewriters, creating sheetmetal, formica enclosures, installing frosted lighted buttons and other details that drove up the project complexity and cost, but also increased the experiential fidelity and thus my ultimate satisfaction.

I had essentially zero hardware design experience or training at the outset of this project. I have poked and fooled with electrical and electronic items all my life, but with very limited understanding. I could look at simple circuits and understand them from a basic DC standpoint - trace the wiring and the switches. I had a rudimentary understanding of an RC constant but otherwise didn't grasp AC circuits at all. I understood basic logic gate types and ways to simplify or understand their connections, but that was nearly all I knew. Ohms law was the limit of my analytical toolkit for electronics. I could put kits together (thank you Heathkit and others) and could make crude modifications as long as I didn't need to calculate specific values or do too much engineering.

My entire working life I was exposed to hardware and would have loved to be capable of designing, modifying and deeply understanding it, but didn't have the skills. This project was a means of diving in and acquiring those skills, learning by doing, and having a driving goal that would keep me engaged until my understanding rose to levels where I could accomplish all the electronics tasks I had always wished I could accomplish.

The resulting designs and devices produced during this project are going to reflect this learning process. Some of the work will not be up to the standards of a working professional electronics engineer. As I built up skill in digital hardware design and VHDL coding, there were times when I used poor practices out of ignorance, or because I hadn't reached the skill level to properly see and implement the correct approach. I have tried to go back through the project periodically and improve sections more in line with current best practices.

This blog documents the 1130 effort, not the learning journey I undertook as a necessary part, but there will be places where I allude to my personal learning, perhaps covering some detail that is blindingly obvious to those readers who are experienced digital designers, but when it wasn't blindingly obvious to me as a tyro, I suspect it might not be obvious to the readers who are not engineering professionals.