Sam Battle's Core Rope Memory Drum Sequencer Builds on Classic NASA ROM Technology

Maker and musician Sam Battle, of Look Mum No Computer, has put together an electronic drum machine that uses core rope memory, having been inspired by a vintage auto-dialer.

"I got this from Mike's Electric Stuff, and he covered it in a video then we did a bit of a swap and I took this to the museum to plug it into the telephone exchange," Battle explains of the device, which inspired his retro-memorial creation. "It's an old Soviet Sierra Auto-Dialer, but it's got quite a bit of an interesting thing: You see, the way it stores its numbers [is] the same technology that was used in the Apollo Guidance Computer for the ROM and such. It's called rope core memory."

First deployed, as Battle explains, by NASA for both early Mars space probes and the Apollo Guidance Computer, core rope memory was a twist on magnetic-core memory designed for read-only operation. Unlike other form of data storage available at the time, core rope memory was robust, compact, and high-density by the standards of the day — being able to store 72kB of data per cubic foot to a mere 4kB for rewritable magnetic core RAM.

In the auto-dialer, the core rope memory was used to store a selection of telephone numbers for later retrieval — but Battle had a different plan for the technology, putting together a 3D-printed core rope memory module to form the heart of a musical sequencer.

The resulting device isn't likely to hit the 72kB-per-cubic-foot storage density of traditionally-woven core rope memory, however: as a display piece as much as a functional sequencer, Battle's machine uses large ferrite toroids with highly-visible wires threaded through, serving the same purposes as the much more compact toroids of traditional core rope but in a much more visible manner.

Elsewhere on the wooden panel,which serves as the device's housing is an electromechanical switch to act as the pattern selector, comparators and oscillators based on 555 timers, a coil driver, a drum voice bank, and an amplifier boost the output and make the sound happen. A handful of LEDs provide visual feedback as to the machine's operation, to complete the build.

"This was not the machine I originally had in mind," Battle admits. "I hope to make a version two which is a more performative sequencer. As this design does not lend itself to live sequencing. The next machine is a bit more involved circuit wise as it adds another dimension to the wire. scanning. But if I get the rope core flame lit again there will be another."

Those interested in building their own can find more information in Battle's video, as well as in the schematics published to the Look Mum No Computer website — though the latter come with the warning that it's a "dodgy idea" and builders should not "expect the world" from the device.