Sequencing The Vintage Way

For most of us, an 8-bit microcomputer means one of the home computers which set so many of us on our way back in the 1980s. But this ignores an entire generation of 1970s 8-bit machines which filled the market for affordable office and industrial desktop computing before we were seduced by Pac-Man or Frogger. It’s one of these, an SWTPC 6809, that’s found its way into the hands of [Look Mum No Computer], and in direct contradiction to his branding, he’s used it to control a synthesizer.

As you’d expect from the name, the computer hides a 6809 processor, and comes from the end of the 1970s when that chip had been released in an effort to stave off the market threat from the likes of Zilog and MOS Technologies. It has an SS-50 bus motherboard, and the saga in the video below the break is as much about the production of a custom DAC and trigger port for it to drive the synth as it is about troubleshooting a four-decade-old computer. It’s a credit to SWTPC that the machine is largely working after all this time, however it succumbs to some damage during the development of the interface.

At the end though, there’s a fully functional sequencer on a 1970s computer, playing some pretty good electronic music from an analogue synth. This is EXACTLY the future we were promised, back in 1979!

Long-time readers will know this isn’t the first SWTPC that has graced these pages.

5 thoughts on “Sequencing The Vintage Way

  1. Ah, the old days…
    I once had an Appple II and a cheesy drum rompler with midi input. The Apple II was just fast enough to spit out midi via its game port. It needed a nop-tuned machine code call which was just a few bytes long. Above that a basic program featured as pattern sequencer (and the machine code loader, remember data/poke?). It worked, and it was one of my first “I can do it” experiences.

    1. Memories, indeed.

      Not counting a PAiA hardware 12-step sequencer, I had a Radio Shack CoCo II (Colour Computer) with a hardware MIDI interface. And, I believe, Lyra software.

      Fun stuff. I coulda become the next Vangelis, if not for my complete lack of musical talent or inspiration.

  2. I knew a guy who had bought an SWTPC. He wanted someone to build the RAM boards for him and test the machine. I offered to do it and got the machine for a month. This would have been in the summer of 1974, when I was in college. I had a Teletype to interface with the SWTPC and built the two memory boards and ran some code to burn them in for him. It was a sad day when I had to return it…

    Later, I built my own 6800 platforms with much denser RAM chips (I think the SWTPC used 2102s?) — 2kx4 IIRC!

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