Whenever I tell people I’m building a relay computer the overwhelming response is … why on Earth would you want to do that?! Or alternatively, as a work colleague delicately put it to me yesterday, if you go to the front of your house there’s a big block of wood that opens — it’s called a door — if you go through it you’ll discover pubs and things. They’ve all got a point though, this project will be very time consuming and I’ve not particularly got a use in mind for the resulting jumble of wires. In fact it’s difficult to think of a real use for it as I’ll be left with something that could be outperformed by a pocket calculator (not a scientific calculator mind, more the kind you might find in a Christmas cracker). So why would I invest lots of time and effort in to making a relay computer? Well, as they say (rather tritely) it’s the journey not the destination.

I’ve always been interested in electronics. As a child I would delight in taking things apart to see how they worked; always marvelling at those green circuit boards within with all the variety of bits and bobs soldered to them. This intrigue was all usually at the expense, literally, of my parents as I’d tend to have far more success taking things apart than I would putting them back together again. Naturally as I got older I started to learn a little more and started putting shop bought kits together — usually complete failures as I’d cook the components with my clumsy soldering but there were some successes. I didn’t stick around for A levels at school but after a couple of years working in reprographics for a local screen printers I decided it was time to get back in to education and learn some more … electronics still the natural choice for me. Unfortunately the time I decided to get on with electronics was also the time the college canned the courses through lack of interest. Given this I decided to plump for my second interest … software development.

So here I am now thirty-six years of age and programming computers is now my day job and has been since college. Actually, being a software developer (or computer programmer, software engineer or whatever it is we’re calling ourselves this season) has become my first love now; I find it deeply satisfying. My interest in electronics has never really gone away though — it’s been hibernating — waiting to be awoken again when the right project comes along. Trouble is I’ve never had anything I fancy making … then it hit me … I use computers day in day out but I don’t really have all that much of an appreciation for how they really work under the hood. Even when I was a kid and computers were much simpler you could understand the overall architecture but it was all just theory in a way. I remember my parents bought me a spectrum +2a for the not inconsiderable sum of £129.99 (we actually got through three of them — each week taking the latest one back to Dixons for a replacement due to tape deck faults). Once I’d exhausted all the games that came with it I got in to programming in BASIC and then eventually I delved into assembly language. That gave me a real feel for what the computer was actually doing but it still seemed quite advanced and a long way from where computers had actually started from. The seed was therefore sown — if I wanted to get a feel for where computers had come from I should get acquainted with some really old computers — if I really, really, wanted to get a feel for where computers had come from I should have a go at building something like a really old computer.

It just so happened a few months later that on a visit to see my folks ‘oop north’ I popped into the National Museum of Computing (highly recommended if you’re of a certain age and want to be filled to the brim with nostalgia). They had recently completed the Harwell Dekatron restoration (also known as WITCH), restored so successfully in fact that the computer was happily operating away to itself on the day I visited. There’s a certain beauty to the machine — all the flashing lights and clicking relays. It’s certainly not dainty — you wouldn’t want it sat on your foot — but there’s just a certain something about it. It was at this point where I decided to kill all my birds with one boulder - I would create something that had a nod to the machines of this era; learn more about electronics along the way (using the old fashioned learning method of trial and error) and get that first hand understanding how computers really work. Even better I’d get to make my own assembler and if I really, really, fancied it might even make a high level language compiler for it (assuming I haven’t died of old age by then of course).

So there we have it — this is a project that’s about satisfying curiosity and interest; a project about exercising creativity and problem solving; a project about making theory concrete and tangible. Ultimately it’s a hobby — I’ll still go to the gym, socialise, get nicely drunk at the pub — but it’s something I’m looking forward to and even a little bit excited over. Soldering irons at the ready? Yes? Then off we go …

Published Nov 02, 2013
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