In 1969, Harry amazed everybody with a little electronic gadget he’d built which, using the primitive digital integrated circuits of the time, generated random music, played it through a speaker, and flashed lights on its front panel. It was precisely what people expected computers to do, based upon portrayals in the movies and on television, and yet it could be held in your hand and was, internally, very simple. He explained how it worked, and I immediately knew I had to have one. Digital electronics was in a great state of flux at the time, with each manufacturer launching their own line of integrated circuits, most incompatible with one another, so there was no point in slavishly reproducing Harry’s design. Starting from the concept, I designed my own gadget from scratch, using Signetics Utilogic diode-transistor small scale integration integrated circuits which were popular at the time but shortly thereafter made obsolete by 7400 series transistor-transistor logic (TTL). The architecture was identical to Harry’s device, but I opted for more with-it and less power-hungry light-emitting diodes (LEDs) for the display instead of the incandescent bulbs he used. I built the electronics assembly on a sheet of perforated board using wire-wrap fabrication (some people look down their noses at wire-wrap today, but it was good enough for the Apollo Guidance Computer and almost every mainframe backplane of the 1960s, and my wire-wrapped electronics works perfectly fifty years later.)

Little did I imagine, when designing and building the Mind Grenade hardware in 1969, that fifty years later I’d be emulating it on a computer which ran more than a thousand times faster than the one I used in my day job at the time and, furthermore, was sitting on my own desk. But here we are. Thanks to HTML5 and JavaScript, it is now possible to emulate the hardware Mind Grenade entirely in software that runs within any modern Web browser. Below is an abstracted version of the Mind Grenade front panel. Press the power button at the bottom to get things going. The slider at the left controls the pitch and the slider at the right sets the rate at which the notes play. The check boxes below the lights select any of the 16 possible tunes that can be played.

source: HN