And it wasn't just a 4KB "stick" of RAM or something, it was literally magnetic rings threaded onto wires called Magentic Core Memory. Further, 4 KB implies that it was 4096 bytes, but it was actually 2048 "words" consisting of 15-bits (+1 parity bit) [source]. 2048 words requiring 16 bits each means 32,768 magnetic rings weaved onto tiny wires. Oh, and another fun detail about magnetic core memory is that if you read a value, I.e check to see if one of those magnetic rings is set to 0 or 1, that is a destructive operation. So if you wanted to read without deleting, you have to read and then immediately rewrite.