Core rope is long obsolete, and I hadn't even heard of it prior to studying Apollo. In contrast, read-write "Core" was very common in the computers I used in the 1970s.
So when Hunchbacked started dissing core rope, that gave me a chance to study and understand how it worked. It was actually a very clever design, using what you might call "magnetic logic" to decode the address bits.
Wires carrying the address bits and their logical complements were threaded through the cores in such a way that for any input, exactly one core did not have at least one energized address wire. The rest were all driven into magnetic saturation, blocking the coupling of a readout pulse to the sense wire. Only the addressed core, which remained unsaturated, could perform this coupling.
Starting in the mid-late 1970s there were medium-scale-integrated circuits that were custom made for address decoding, but they didn't exist in the 1960s. If the AGC designers had had to build a address decoder from the standard dual 3-input NOR gates used in the rest of the AGC, I figured they would have needed thousands of packages. The entire computer had only several thousand.
