When I was in my late teens and early twenties, the computers I used were all based on ferrite core memories. It's a pretty unique, now mostly forgotten technology that relies on magnetic hysteresis to flip small toroid "cores" made from a special type of hard ferrite (the toroids used to make

Electronique - historique : introduction mémoire à tores de ferrites (core memory), le magnétisme

Conception et réalisation d'une memoire rapide à tore magnétique. 1960