I can't recall the term for those flywheel things. But they are used a lot for stuff that needs brief *massive* power surges.

I've got a 256 byte core plane not 5 feet from me. It's the same size as a 5.25" floppy (in fact, it's stored with some)

It'd take a massive EMP to effect the core plane. More likely to have problems from the induced currents in the rest of the computer.

I also have a magnetic bubble "experimenters kit" that Intel used to sell. I think it's 256k or so.