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Apollo Core Rope Memory (Apollo Guidance Computer Part 30)

CuriousMarc2 HN recommenders · 2023–2026
759K views · documentary · evergreen · Uploaded 2023-10-27

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.

HN commenters recommend it as the deepest explanation of how AGC rope memory works and how it differs from core memory.

History of computingSpace exploration & spaceflightDemoscene & retrocomputing

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4 comments from Hacker News

@dadadad1002023 · in “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] [VIDEO]

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@dadadad1002023 · in “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. [VIDEO]

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@FullyFunctional2023 · in “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: [VIDEO]

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@alnwlsn2026 · in “Remembering Magnetic Memories and the Apollo AGC”

As seen on Curious Marc, where some real AGC core rope ROMs are read: [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).

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