Each ROM word is a wire. If the wire goes through the first magnetic core, its first bit is a one; if it skips the core, its first bit is zero, and so on. Each of the 36,000 words of ROM needed to be threaded through these cores by hand. Amazing.
(I imagine it was chosen because it's much more resilient to cosmic rays flipping a bit. But it's pretty much impossible to alter the program without creating the whole thing from scratch. The ultimate spaghetti code!)
http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/a...
Each ROM word is a wire. If the wire goes through the first magnetic core, its first bit is a one; if it skips the core, its first bit is zero, and so on. Each of the 36,000 words of ROM needed to be threaded through these cores by hand. Amazing.
http://en.wikipedia.org/wiki/Rope_memory
(I imagine it was chosen because it's much more resilient to cosmic rays flipping a bit. But it's pretty much impossible to alter the program without creating the whole thing from scratch. The ultimate spaghetti code!)