Technology

BBC Micro Archive

Three Decades of a Beeb

I bought a BBC Microcomputer in mid-August 1982. It was of Model B specification, though this was via an upgrade from an original Model A that had been done by the London based retailer. Over time, I added various standard peripherals such as dual floppy disk drives, an Epson FX80 printer and the Acorn Speech System (with the dulcet tones of BBC newsreader Kenneth Kendall).

I continued to use my Beeb for nearly thirty years until January 2012, when I finally gave it away. Before I passed the computer on, I transferred the data from my floppy disks to a PC. The disk images contained all the programs that I or various friends had written, been given or otherwise collected - plus loads of documents. I worked on the principle of getting rid of junk hardware, but preserving all the soft stuff!

Custom Hardware

Electronics had been a hobby of mine long before I got my BBC Micro. I was also interested in music, but more in terms of creating weird sounds rather than becoming a virtuoso player (I achieved grade 1 violin, but that was about as far as my formal training got!). Many electronics magazines contained designs for analogue synthesisers, so I was keen to have a go at building one. However: where would I get a keyboard from? Then, in 1981, the disused Presbyterian church in Maryport was being knocked down. On September 4^th, I ventured into the half-demolished rubble and retrieved the huge wooden keyboard from the remains of the organ! I cobbled together some contacts for each of the 58 keys, complete with a resistor ladder, which could be used to drive a Voltage Controlled Oscillator. I build an entire (monophonic) analogue synth on breadboards and had endless fun making strange noises.

Once I'd bought my BBC Micro, I decided to build a new interface - digital this time - to connect the keyboard to the Beeb. The design was relatively simple, using the BBC's User Port (at address &FE60). Writing to the lower 6 bits would select a key, then reading the top bit would give a result showing if that key was pressed. It was then straightfoward to write software to access the keyboard and play music using the BBC's sound chip (with up to three notes of polyphony).

In my final year at university, my engineering project was "A Digital Audio Effects Processor". I built this using a "Profi-kit 2" Motorola 68000 based development system, with a Ferranti ZN432E A/D and a National Semiconductor DAC1022 D/A (both 10 bit). The results were pretty good, but the audio bandwidth was a bit limited due the processor requiring rather too many clock cycles (up to 32!) to perform many of its operations.

After finishing university, I built A/D and D/A converters for my Beeb. I dropped down to 8 bits, using Ferranti ZN427 and ZN428 chips. I never got round to making a proper PCB, so the design continued on breadboards right up until I disposed of the whole lot! I used the BBC Micro 1MHz Bus to interface the hardware to the computer. Writing to memory location &FCC0 would send output to the D/A converter; reading &FCC0 would return the current value from the A/D converter. Simple! Software I wrote included effects such as reverberation/echo, frequency transposition, emulation and synthesis. All of this took place in the first half of the 1980's.

Other, less custom, hardware I had included: a joystick connected to the on-board analogue port (with additional potentiometers on the third and fourth inputs); a light pen (though that never really worked satisfactorily); an EPROM programmer to allow me to burn my own custom sideways-ROMs; a 32K sideways RAM system that a friend donated to me (in 1986) after his old Beeb expired and he upgraded.

Photographic Evidence

I only have one, rather poor, photograph showing my BBC Micro with the church organ keyboard. It is from I circa 1983 and I've included it here in an attempt to show that I've not just been writing fiction!

You may also note my ultimate A/V system of the era, consisting of: a Tandberg Series 8 mono reel-to-reel tape deck; my brother's old record deck (not that I actually owned any vinyl discs!); a Decca CS1830 hybrid valve/semiconductor colour TV; a Pye "FenMan II" valve wireless (which had VHF FM, hence "FenMan"); a really cheap and nasty cassette recorder; all linked together via my own source switching unit built into an old biscuit tin.

Software

Nearly all of the software I preserved can be run in a suitable emulator on rather more modern hardware. For my own use, I have a version of BeebEm which I modified to also emulate my custom hardware (see above). For most of the software, though, the programs can be run using the jsbeeb JavaScript BBC Micro emulator. This doesn't, currently, seem to emulate the BBC Speech System (nor, of course, my own additional hardware!).

A selection of disks containing programs vaguely suitable for public consumption is provided below. The Disk Image name should give some idea of the types of programs on each disk. Clicking on the description should load and boot the disk up in an external instance of the jsbeeb emulator - noting that JavaScript will need to be enabled for that site.

Enjoy!