YouTuber Igor Brichkov has made a core rope memory using ferrite cores and wire, which was famously used in early UNIVAC computers and for the Apollo guidance computer, as a RAM alternative in the 1960s and 1970s before the creation of EEPROMs and flash memory.
Although the cores are magnetised to create core memory, the rope memory serves as a sensor, with a signal trying to reverse the polarity of the cores and an inhibit signal preventing this from happening, and then a sensing wire detecting a blip when the core changes polarity.
Brichkov explains that rope memory is better than core memory as it can store more data, albeit less efficiently, but it has seen a resurgence as a fun project to undertake.
