Reincarnated Return of the HRRG 4-Bit Computer (Part 1)


In some cases I wonder whether or not I’m the only a single who has passion initiatives that drag on for yrs, moving back and forth amongst the metaphorical back again-burner and entrance-burner of my awareness span, evolving and transmogrifying as the months change into months and the months flip into many years and—in the circumstance of some of my creations—the many years turn into decades.

These types of has proved to be the situation with my Heath Robinson Rube Goldberg (HRRG) laptop, which was initially supposed to be an 8-little bit machine when it was initial conceived deep in the mists of time.

This bodacious beauty is named in honor of British cartoonist and illustrator William Heath Robinson (1872-1944) and his American counterpart Reuben Lucius Goldberg (1883-1970). Equally of these gentlemen were being famed for building illustrations of cunning contraptions whose ambitions have been to carry out seemingly very simple duties, but whose realizations done reported duties in exceedingly convoluted approaches.

This all started when I saw a relay-centered laptop or computer made by Professor Harry Porter III, who was a lecturer at Portland Condition University at that time (he may perhaps even now be there for all I know). (You can understand extra about Harry’s machine here.) I cherished the seem of the relays clicking, and I also loved the way Harry presented his machine in a sequence of glass-fronted, wall-mounted picket cabinets. Nonetheless, I was not so eager on the bundles of wires linking the cabinets with each other.

To be straightforward, I’d had the thought of building a relay pc lurking in the again of my head for some time. I’d even gone so considerably as to obtain some secondhand textbooks on making relay-dependent logic relationship from the 1950s and 1960s. The difficulty was that, in addition to inspiring me, Harry’s generation also dampened my spirits mainly because I did not want to do some thing that an individual else had already carried out, if you know what I indicate.

This is what led me to my primary large-stage principle of the HRRG Personal computer, which was to develop my device as a series of glass-fronted, wall-mounted wooden cabinets, like Harry’s, but with every single of my cupboards containing a part of the laptop or computer understood in a various implementation engineering, such as (but not limited to) relays, vacuum tubes, discrete transistors, jelly-bean (7400-series) integrated circuits (ICs), mechanical logic, magnetic logic, pneumatic logic…to name but a several. Also, in maintaining with the HRRG philosophy, we would do away with the bundles of cables, implementing any inter-cabinet communications by means of a wi-fi mesh community.

Picture supply courtesy of Joe FarrElectronics Heath Robinson Rube Goldberg (HRRG) computer Max Maxfield

The HRRG 4-little bit personal computer emulator and printer.

I in fact place a sizeable amount of money of assumed into this project, such as buying several things I planned on using, this kind of as thousands of 1960s teeny-very small ferromagnetic cores I picked up for a several pounds from somewhere in Jap Europe (I planned to use these to implement a magnetic logic cabinet alongside with a magnetic core memory cabinet).

Regretably, I’m a bear of small brain, as Pooh Bear could possibly say. Also, I have a small interest span and I’m effortlessly distract…SQUIRREL!!! As a consequence, my focus wandered on to other tasks.

After many years’ hiatus, I was introduced to an engineer named Joe Farr. Joe and I share numerous pursuits, including a love of retro personal computers. Because Joe is so central to the current incarnation of the HRRG, I requested him to send me a couple of text I could use to introduce him, and he replied as follows:

I’m a keen electronics, computer, and radio novice. The moment I’d completed my (formal) schooling in the 1980s, I started my job as a laptop or computer programmer for Nixdorf Desktops positioned in Manchester, England. After various a long time, I relocated south (mostly for the improved local weather), operating with main engineering firms on software program, components, telephony, and mobile info devices. Now, after many several years in the freelance entire world, I’ve settled down in an idyllic region hamlet just outdoors Cambridge the place I tele-commute to my comprehensive-time (day) job as a senior software and hardware engineer with the London Ambulance Service.

Immediately after extra e mail discussions than I treatment to contemplate (this was right before video clip conference calls turned the norm), the HRRG had remodeled into a 4-little bit device because we believed that would be much more entertaining. Also, we established that a 4-bit laptop or computer would make a lot more feeling as an instructional instrument.

The present principle consists of having a process clock cabinet, a CPU cabinet, and a bunch of memory cabinets. The concept is that hobbyists and significant university learners would be in a position to develop memory cabinets that contains as tiny as 1 4-bit word of memory applied in the technological innovation of their alternative, and that these memory cupboards would then speak to the key CPU cupboard.

Even much better, as part of this, Joe has made an emulator of the overall procedure that runs on a Personal computer. This signifies you can initial make a virtual memory cupboard that talks to the virtual CPU, and later develop a bodily implementation of your cabinet that talks to the virtual CPU (or a physical model of the CPU if you occur to have just one).

Graphic courtesy of Joe FarrElectronics Heath Robinson Rube Goldberg (HRRG) computer Max Maxfield

The HRRG 4-little bit computer system assembler.

Just to insert a excellent major dollop of product on to the top of the metaphorical cake, Joe and I outlined our very own assembly language, immediately after which Joe whipped up an assembler. As we see in the screenshot previously mentioned, the assembler itself appears to be like like it is operating on a digital Sperry Univac Uniscope 200 knowledge terminal.

So, as you can see, Joe and I put a significant sum of exertion into this undertaking, until…SQUIRREL!!! What can I say, we both got distracted with other jobs, and a layer of dust began to improve on top rated of the strategy of the HRRG. And then…

Sometime in early 2021 I acquired an e mail from an electronics engineer named Nils van den Heuvel who hangs his hat in the Netherlands. Possessing operate throughout some of my before writings on the HRRG 4-little bit laptop, Nils mentioned he was fascinated in building an FPGA-dependent implementation.

So, Joe, Nils, and your humble narrator started out to have weekly conferences. There is almost nothing like striving to construct something to reveal any holes in your design and style, and the HRRG was no exception. As a result, we have advanced the CPU’s sign-up set and instruction set into one thing that I genuinely imagine is truly fairly tasty. I shall share a lot more on these subject areas and introduce Nils correctly in my subsequent column. In the meantime, as normally, I welcome your comments, inquiries, and recommendations.


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