Core rope memory

Core rope memory is a form of read-only memory (ROM) for computers, first used in the 1960s by early NASA Mars space probes and then in the Apollo Guidance Computer (AGC) designed and programmed by the Massachusetts Institute of Technology (MIT) Instrumentation Lab and built by Raytheon.

Core rope memory test sample from the Apollo program.

Software written by MIT programmers was woven into core rope memory by female workers in factories. Some programmers nicknamed the finished product LOL memory, for Little Old Lady memory.[1]

Memory densityEdit

Rope memory from the Apollo Guidance Computer

By the standards of the time, a relatively large amount of data could be stored in a small installed volume of core rope memory: 72 kilobytes per cubic foot, or roughly 2.5 megabytes per cubic meter. This was about 18 times the amount of data per volume compared to standard read-write core memory: the Block II Apollo Guidance Computer used 36,864 sixteen-bit words of core rope memory (placed within one cubic foot) and 4,096 words of magnetic core memory (within two cubic feet).[citation needed]

Data units per cubic foot Data units per cubic meter
Bytes Bits Bytes Bits
Core rope ROM 72 KB 576 Kbit ~2.5 MB ~20 Mbit
Magnetic core RAM 4 KB 32 Kbit ~140 KB ~1 Mbit


  1. ^ Directed and Produced by: Duncan Copp, Nick Davidson, Christopher Riley (2008-07-07). "The Navigation Computer". Moon Machines. Episode 3. 22:40 minutes in. Science Channel.

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