It's one of those technologies that makes you wonder what would've happened if they just kept advancing it instead of outright replacing it with something else entirely. How tiny could cores be made? Could modern chip manufacturing techniques be used to make nano-scale core memory?

See also: vacuum tubes (there were attempts to miniaturize them to try to compete with transistors), CRT displays (there were some wild concepts like a flat-panel CRT where the gun is at the top and the beam makes a 180° turn at the bottom before it gets deflected into the screen; also late CRT TVs that had slimmer tubes).