Day 338, Retro computing, it's all the rage

I've built a replica of a 1970s computer, from a kit.

Why build a replica of an old computer from a kit I hear the voices in my head ask.

Well, it’s like this.

I’d always been fascinated by computers, maybe it was something to do with seeing 2001: A Space Odyssey at the pictures at an early age, maybe it was seeing the flashing lights and spinning tape reels in various ancient spy films on TV, maybe my subconscious had spotted something important and wouldn’t let go. Perhaps that's it, scary pseudo-sentience and answers produced by almost magical activity.

It was the development of an obsession. Even my cardboard egg-box car had a cardboard computer in it. The cardboard computer had a slot in it where I would put a cardboard tape for loading data, about the size of a Dictaphone tape - I’d never seen one of these things, I invented it, clearly. Where's the payout for the theft of my IP?

Maybe there wasn’t as much in the way of electronics involved as Turing and Bletchley Park had, but it was the concept. I’d prototyped the idea in cardboard but didn’t have the technology available to recreate it.

A few years after this, when I had enough money to buy an electronics magazine every few months, I noticed there were kit computers being sold in the ad pages. Eventually there were articles about them in the electronics mags, and soon this spawned a whole shed-load of magazines devoted entirely to this new area of electronic interest.

The first computer I touched was in a physics class at school sometime in the late 1970s. It was a KIM-1, we didn't do a great deal with it, in fact we weren't even allowed to touch it. It was a single board machine, housed in a fancy wooden box that someone had made which even included dovetail joints. There was a sheet of perspex on the top so that the whole of the board was visible and this had a square cut out of it so that the keypad was accessible.

The moon rises and falls, many seasons pass. And then...

Recently it occurred to me that building the KIM-1 couldn't be that difficult, so I bought a bunch of ICs, the 6502 processor and other parts, and started looking for how to go about designing a working copy and looking for a circuit board layout. It was then I discovered that the world had passed me by and the KIM-1 had been recreated already by people with much superior electronics skills to mine. So I bought one.

All I had to do was assemble the hell out of it, not zap anything with my enormous static charges, and solder the components to the board.

After assembly but before insertion of the ICs the testing amounted to:

A visual scan of all connections to make sure they looked clean, tidy, and fully soldered.

Powering up to make sure the power light comes on.

Checking the input voltage and the output voltage of the voltage regulator.

Checking the voltage at vcc and ground on each of the IC sockets was 5v (the respective IC reference sheets tell you which pins.)

Checking the output voltage on the 1Mhz oscillator.

All tests passed successfully, ICs inserted, power on - and bloody hell it worked first time.

Here's a short video of the test program, a clock, that I entered via the hexadecimal keypad.  It was just before quarter past six in the evening, as you can see.

This doesn’t mean that I won’t have a go at building a completely original 6502 based computer at some point - if it is possible for any of this to be completely original.  There are plenty of resources out on the internets to help design such a thing.  And it’s more likely that I’ll do that than ever be able to fit in an egg box ever again whilst still being a functioning human being.

For official/internal use only:
7575

0-9