Apollo Core Rope Memory (Apollo Guidance Computer Part 30)
Why Hacker News recommends it
HN commenters recommend it as the deepest explanation of how AGC rope memory works and how it differs from core memory.
What it is
CuriousMarc's Apollo Guidance Computer restoration series looks at core rope memory, the ROM that held the Moon landing programs. Mike Stewart builds a custom reader to recover lost AGC programs.
Recommended by 2 HN commenters across 2 different months, 2023 to 2026.
What Hacker News said
Strong rec dadadad100 · 2023-11 · on “The Apollo Guidance Computer”
Obligatory shoutout to curiousmarc and Mike Stewart. I’m stunned by the amount of work that have put into making this national treasure (partly) operational again [0] [LINK] [1] [LINK] [2] [this video]
Recommends dadadad100 · 2023-11 · on “The Apollo Guidance Computer”
Here,s a deep, deep dive into AGC rope memory. My mental model was stuck on core memory until I saw this and finally got the difference. Tl;dr Way higher information density. [this video]
Recommends FullyFunctional · 2023-12 · on “A Vacuum Tube Single Board 1-Bit Computer [video]”
Delay lines are fascinating, but I don't see why this is easier than core memory; seems like you are trading an electronics problem for a mechanical one. Regardless, at the speeds they are targeting, I think delay lines might be difficult. Another interesting option (for ROM) is core rope memory. CuriousMarc has the ultimate explanation: [this video]
Cites alnwlsn · 2026-04 · on “Remembering Magnetic Memories and the Apollo AGC”
As seen on Curious Marc, where some real AGC core rope ROMs are read: [this video] They even have to work around some design mistakes made in the modules in order to read them correctly. Not many living people know more about the AGC than those guys (especially Mike Stewart).