Inside the Apollo Guidance Computer's Core Memory | Hacker News Reader

Inside the Apollo Guidance Computer's Core Memory

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57 pointsNelsonMinar6 comments

If you look at the youtube channel "CuriousMarc" (just search for it, they have multiple restoration videos), you can look at this project in video, the latest video shows their attempt at finding the module's problem via XRay at the end, the other videos detail earlier parts of the operation, including booting up the AGC with original code fed from a ducttape-design FPGA/microcontroller. It's a very interesting video series to follow.

We attempted to find the location of the broken wire with X-rays, but couldn't spot the break. Time-domain reflectometry suggests the break is inconveniently located in the middle of the core planes. We are currently investigating options to deal with this.

Depending on what it was potted with, dissolving the potting to repair it might be feasible. Many others have done this with (admittedly less rare and fragile) not-easily-replaceable electronics before, but it's a difficult and time-consuming process. The 38AWG wire is ~0.1mm so the traditional "pick out bits of potting" method is unlikely to keep the wire intact --- something more like dissolving and gently washing away the compound would be preferable.

We figured that if the break was near the outside of the module, we might be able to dissolve the potting around the break. But unpotting the entire module to search for the break has way too big a chance of breaking more wires or causing more damage.

Great write-up. If you haven't seen it yet I'd highly recommend watching the entire YouTube series (part 6 is linked at the end). Some fantastic engineering!

My dad spent his career as a customer service engineer for IBM. When I was about seven years old, back in the '70s, he took me to work at one of his accounts, the Washington Post. He showed me their room full of mainframe, and opened up a cabinet of core memory, thousands of wires and tiny donuts. Now and then, when I use a thumb drive with hundreds of billions of stored bits, I think of the day when I could see every individual bit in a box almost as big as I was.

Fantastic article. I wish I was born a lot earlier so I could work with these discrete and semi-integrated devices. they looked so much more fun than modern electronics which is just "bus the ICs together".

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