I bought my UK101 on 21st February, 1980. I went to Comp Shop in New Barnet by train from Colchester and came back with my kit, in its cardboard box. I got it working that same evening, although I did find that the “3” key was shorted. I was lucky to be able to diagnose the fault and remove the defective keyswitch! Building the kit took me six hours of soldering.

Remember that the first thing required on start-up was for the user to type in a response to the D/C/W/M? prompt (Disk/Cold start/Warm start/Monitor). If one of the keys was faulty, there might be no way of knowing what was wrong. That was typical of machines of the time, one small failure and the machine won't start up. Of course, few amateurs had test gear to diagnose faults in this type of equipment and substitutions were impossible with just one machine.

This photo shows my UK101 as it is today. It includes all the extra hardware that I added to it over the period 1980-1985. The case, made of plywood by my father, was originally black but I later sprayed it the bright yellow that you can see here. The plywood lid is covered with black leathercloth and just rests on top of the case.

Click on the photo to see a bigger version, with the various add-ons and modifications labelled and described.

Software for machines like the Compukit was nearly all written by the users. I typed in listings from magazines, I modified BASIC programs for other machines but I also wrote a lot of code myself. Nearly all my UK101 software is games! The rest is driver code for the various bits of weird hardware that I mentioned above. Much of it falls into the category that we now call “demo software”, programs that do little more than show what the hardware is capable of.

Of course, I also wanted to find out how the UK101's own software worked. I still have a complete disassembly of the BASIC ROMs, the Monitor ROM and the Extended Monitor, all done on a 110 baud Teletype ASR-33. Having done that, I set about writing a new and improved monitor ROM which I eventually put into a 2716 EPROM.

I took my UK101 along with me to university — Westfield College in Hampstead, north London. I wrote a simple terminal emulator and connected it up to the college's timesharing system, a Prime P750. Meanwhile, other 6502-based systems became popular, such as the BBC Micro and the Commodore 64. However, having used Unix on a PDP-11/44, the UK101 began to look a bit limited and it got used less and less.

The machine still works and is now part of my Compukit Museum. I occasionally start it up and run some of the old software. Recently, I fixed a niggling problem in the 16k RAM expansion card, which caused subtle memory errors. But on the whole, the machine is too deeply modified to do very much more with it on the hardware side.

In 2010, I took my original UK101, along with two other machines, to Bletchley park for the first Vintage Computer Festival in the UK. It appeared in several of the reports on the show, including this one from ZDNet, another from M1NER. I wrote about it on my old blog, too: Vintage Computers and Bubble Cars.

It's now more than 40 years since Practical Electronics published the UK101 design, and 41 years since I built my machine. Meanwhile, personal computing has changed beyond all recognition.