Hacking Apollo Hack Chat

Apollo was a hack from the Earth to the Moon

Wednesday, April 22, 2020 12:00 pm PDT Local time zone:
Hack Chat
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The Apollo Guidance Computer team will host the Hack Chat on Wednesday, April 22, 2020 at noon Pacific Time.

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When President Kennedy laid down the gauntlet to a generation of scientists and engineers to land a man on the Moon before the close of the 1960s, he likely had little idea what he was putting in motion. The mission was dauntingly complex, the science was untested, and the engineering was largely untried. Almost everything had to be built from scratch, and entire industries were born just from the technologies that had to be invented to make the dream come true.

Chief among these new fields was computer science, which was barely in its infancy when the 1960s came along. By the end of the decade and the close of the Space Race, computers had gone from room-filling, power-guzzling machines to something light and capable enough to fly men to the Moon and back. The computers that followed all built on the innovations that came about as a result of Apollo, and investigating the computers of the era and finding out what made them tick is an important part of our technological culture.

That's where the retrocomputing Dream Team of "CuriousMarc" Verdiell, Ken Shirriff, Mike Stewart, and Carl Claunch come into play. Together, they've poked and prodded at every bit of Apollo-era hardware they could find, including a genuine Apollo Guidance Computer (AGC) that was rescued from the trash. What's more, they actually managed to restore it to working condition with a series of epic hacks and sheer force of will.

Marc, Ken, Mike, and Carl will stop by the Hack Chat to talk about everything that went into getting the AGC working again, along with anything else that pops up. Come ready to have your Apollo-era hardware itches scratched by the people who've been inside a lot of it, and seen what it took to make it to the Moon and back.

  • Hack Chat Transcript, Part 3

    Dan Maloney04/22/2020 at 20:22 0 comments

    carlclaunch511:02 PM

    When Ken asked if I was interested in joining the project, it didn't take a microsecond to decide yes

    I hate to do this, but we've been at this for an hour and if any of our guests need to get back to work, we should let them go. But this has been really fascinating, and I really want to thank Marc, Ken, Carl, and Mike for coming along today and sharing their insights and experiences. Feel free to keep the discussion going as long as you'd like, of course - the Hack Chat is always open.

    Mark VandeWettering1:03 PM
    Thank you all. Really interesting and inspiring!

    Ken Shirriff1:03 PM
    Thanks for setting this up, Dan.

    simon.dancose1:03 PM
    Great stuff! Thank you.

    Mike Stewart1:03 PM
    Thanks Dan! I'm happy to stick around if anybody has more questions

    Dag Spicer1:04 PM
    Really great way to spend lunch!

    hb9xar1:04 PM
    Thank you for this interesting session.

    curiousmarc1:04 PM
    Thanks Dan for the opportunity. I can stay on a little more but I'll have to go soon.

    Diego Garcia del Rio joined  the room.1:04 PM

    Ken Berkun1:04 PM
    Thank you all!

    Peter Bosch1:04 PM
    was awesome to be able to ask some questions here :) you guys did a great job at the whole thing

    carlclaunch511:04 PM
    I have no work, only hobbies so I will stay on also

    Diego Garcia del Rio1:04 PM

    Andy Geppert1:05 PM
    Fantastic work AGC restoration team!

    Thanks all! I'll wait a while to pull the transcript, in case there are any more interesting bits.

    And don't forget next week we'll be sitting down with Ben Krasnow from the Applied Science YouTube channel, to talk about Citizen Science.

    Diego Garcia del Rio1:06 PM
    Thanks everyone! its amazing to see what you guys did!!! and surprised to find out most of you don't have "formal" EE background... yet do more low level stuff than most EEs I know...

    curiousmarc1:06 PM
    Oh cool. Ben is such a fascinating guy! Is it on the same chat next week?

    Andy Geppert1:07 PM
    I've gone into the rabbit hole with core memory and I am working on a kit for those who are interested. I aim to have some produced this summer (just received another prototype batch of PCBs 20 minutes ago!). Would appreciate your feedback if you are interested in exploring core memory. (shameless plug... but you all are likely to be interested in this sort of thing!).

    carlclaunch511:08 PM
    @Andy Geppert Indeed we are all core memory afficianados

    Mike Stewart1:09 PM
    oh cool! what cores are you using?

    Andy Geppert1:09 PM
    "target market?" if that's fair to assume!

    Andy Geppert1:10 PM
    They are 1mm OD from somewhere in Europe via good ol' eBay. NOS I'm guessing.

    carlclaunch511:10 PM
    yes. Have an Arduino shield core memory board project I bought, but also worked on core more directly. Saw a great hack where someone put lighting to visualize the state of the cores, as an overlay.

    Andy Geppert1:10 PM
    It's soooo satisfying to weave them together and have it actually work.

    carlclaunch511:10 PM
    Yes to target market too

    curiousmarc1:11 PM
    @Andy Geppert Nice! How far can you extend this? I have two Russian memory core planes that I'd love to turn into a working demo display. A 4k plane and a less dense and probably better suited 1k plane.

    Andy Geppert1:11 PM
    @carlclaunch51 I think you saw my proof of concept then, last year after Maker Faire?

    carlclaunch511:12 PM
    oh, that was you at the after party! Yes, loved it

    curiousmarc1:12 PM
    Oh yes I remember it. That was awesome!

    Andy Geppert1:12 PM
    Yes, thanks. Based on the feedback I got, I thought this was worthy to pursue, so this is an extension of that concept to a proper 8x8 bit array. Just think of what you can do with 64 bits!

    carlclaunch511:12 PM
    I have a few minicomputer core memory boards that come with onboard access electronics, much easier than engineering the drive for a naked core board (but less satisfying)

    Peter Bosch1:13 PM
    i've only had some real old core planes to play around with and all of them...

    Read more »

  • Hack Chat Transcript, Part 2

    Dan Maloney04/22/2020 at 20:21 0 comments

    Mike Stewart12:26 PM
    not long -- a guy by the name of George Silver observed the problem at the Cape while testing LM-3, documented it, and reported it. and he knew instantly what had happened

    curiousmarc12:26 PM
    @Mike Stewart But we understand a lot more of it now. It has not been reported correctly by anyone so far as we can tell. It's a horrendously complicated fault.

    carlclaunch5112:26 PM
    The behavior had been observed at both Grumman and during testing, but its impact on the mission wasn't fully realized

    Mike Stewart12:27 PM
    @Jeremy Weatherford essentially yes, but exactly how the circuit breaks down and, more importantly, what the dynamic behavior in response to that breakdown was is something we're still working on

    curiousmarc12:27 PM
    @Jeremy Weatherford Yes that's one of the root causes.

    carlclaunch5112:28 PM
    In simulated landings, there is a very narrow range of load which generates the alarms but doesn't crash the vehicle. Luck was involved.

    curiousmarc12:28 PM
    The equipment that "failed", as it is not so much a failure as an unfortunate system miswiring, was the digitizers for the Rendez-vous Radar position sensors.

    Mike Stewart12:29 PM
    the two power supplies were also at different voltages by the time they reached the CDU -- normal was 28Vrms, but it dropped to 15Vrms when switched to the other supply

    carlclaunch5112:29 PM
    @Mike Stewart oh, even more subtleties and details we hadn't noticed before

    curiousmarc12:30 PM
    It's in the CDU, the Coupling Data Unit, which is a big A/D, bigger than the AGC even. Very complicated.

    Mike Stewart12:30 PM
    for our landing demonstrations I triggered the alarms by using the test connector to halt the computer temporarily every configurable number of memory cycles, and then tuned that number to be a load that would work well for demonstrations

    Mike Stewart12:31 PM
    so things wouldn't get too out of hand :)

    Ken Shirriff12:31 PM
    Another AGC project I'm currently working on is writing an emulator for the Honeywell 1800 mainframe. This computer ran the assembler that created the binaries for the Apollo Guidance Computer. It also created the tapes that were used to put the code into core rope memory.

    carlclaunch5112:32 PM
    Mike's method works equivalently to the real overload because each pulse from the resolver/digitizer would force a hidden instuction thus taking memory cycles

    curiousmarc12:32 PM
    @Mike Stewart Remember how I first made a simple device that produced the pulse stream that was reported in the accident. We connected that to the AGC and that sure ruined your landing.

    Peter Bosch12:32 PM
    did any of the tapes/other sw media survive?

    Mike Stewart12:32 PM
    haha yep

    Mike Stewart12:32 PM
    no, we haven't found any tapes no

    Mike Stewart12:33 PM
    pretty much just listings

    Mike Stewart12:33 PM
    and all of the mechanical/electrical engineering drawings in the National Archives

    carlclaunch5112:33 PM
    and binary in the core rope modules we have been able to read

    Mike Stewart12:33 PM

    curiousmarc12:33 PM
    So it's more subtle than what has been reported. And they were a lot closer to crashing that was also reported. They really lucked out.

    Ken Berkun12:33 PM
    May I interrupt with a background question or two? 1. how do you folks find the time for this (those who aren't retired)? And can you please fill us in on your backgrounds that enabled you to do this fascinating work? Thank you.

    Mike Stewart12:34 PM
    also, while Ken is working on that Honeywell 1800 emulator, I'm slowly taking all of our listings back to punch-card format to feed into it:

    Peter Bosch12:34 PM
    i assume no cores from ground equipment survived?

    carlclaunch5112:34 PM
    @Ken Berkun Ken and I are retired, Marc is semi-retired and Mike is a force of nature

    Mike Stewart12:34 PM
    I just spend all of my time at home, nights and weekends, working on this stuff. And probably spend too many work hours thinking about it

    curiousmarc12:34 PM...

    Read more »

  • Hack Chat Transcript, Part 1

    Dan Maloney04/22/2020 at 20:20 0 comments

    Hello every, welcome to Hack Chat! Today we've got not one but four hosts - CuriousMarc, Ken Shirriff, Mike Stewart, and Carl Claunch. They've done a lot of cool retro hacks, chief among them getting a real Apollo Guidance Computer working again for the first time in 50 years. Welcome all!

    allem.1 joined  the room.12:00 PM

    Maybe you can each tell us a little about yourself to kick things off

    carlclaunch5112:01 PM
    I am retired and able to devote all my time to restoring old mainframes and other vintage technology

    Steve joined  the room.12:02 PM

    hb9xar joined  the room.12:02 PM

    allem.112:02 PM
    I'm retired and looking for new projects.

    @carlclaunch51 - From what I understand, mainframe skills are a growth industry right now. At least for the short term ;-)

    scruzphreak joined  the room.12:02 PM

    Mike Stewart12:02 PM
    I currently write flight software for satellites Capella Space, and devote pretty much all of my free time to Apollo digital archaeology in various forms

    Ken Shirriff12:02 PM
    Hi. I'm a retired programmer and I've been researching vintage computing, reverse-engineering old microprocessors, mining Bitcoin by hand, and studying old aerospace computers.

    Pablo Z. joined  the room.12:02 PM

    curiousmarc12:03 PM
    Hello CuriousMarc here. In real life work on fiber optics at Samtec. Former Intel Fellow. In fantasy life restore old electronics with Carl and Ken and Mike in my over-equipped basement lab.

    KisImre joined  the room.12:03 PM

    carlclaunch5112:04 PM
    @Dan Maloney I ajm focused on the hardware side now, while the current short term interest is in software

    Ken Shirriff12:04 PM
    Marc, Carl, and I have been working together at the Computer History Museum for a while, helping to keep the old IBM 1401 punch-card mainframe running. We also restored a Xerox Alto in Marc's basement. We joined up with Mike to restore the Apollo Guidance Computer.

    Ken Berkun joined  the room.12:05 PM

    curiousmarc12:05 PM
    Actually that's how we all met (save for Mike), working at the Computer History Museum in Mountain View, CA

    carlclaunch5112:06 PM
    We are all volunteers helping with restoration and digital archeology projects

    Ken Shirriff12:06 PM
    Stop by the museum (one quarantine is lifted) to see a punch-card machine running.

    Aaron S. Jackson joined  the room.12:06 PM

    Tomasz Stochmal joined  the room.12:07 PM

    That's still a bucket list trip for me. We had Dag Spicer on last year to talk about CHM and preserving our history. CHM is such a valuable resource.

    Mike Stewart12:07 PM
    And Ken and I were introduced through a mutual friend, because I was about to try to restore an AGC, but didn't yet have any experience working with old hardware at all

    Mike Stewart12:07 PM
    yeah for sure

    curiousmarc12:07 PM
    And if you have an old 1960's mainframe in your basement please let us know

    carlclaunch5112:07 PM
    How about my garage?

    Tomasz Stochmal12:08 PM
    I enjoyed watching your Apollo restoration videos and Soyuz clock.

    Peter Bosch12:08 PM
    I've always been a bit envious of the CHM and the people around it, here in the Netherlands there is no such pool of retro repair knowledge and resources

    Ken Shirriff12:08 PM
    It's amazing how much technology progressed from the IBM 1401 at the museum (1959) to the Apollo Guidance Computer (mid-1960s). The 1401 uses transistors (germanium, not silicon) while the Apollo Guidance Computer uses integrated circuits. They both use magnetic core memory for storage, though.

    Alex Heyes joined  the room.12:08 PM

    curiousmarc12:08 PM
    @carlclaunch51 Yes you have quite a few but you won't let me film ;-)

    DrG12:08 PM
    From "When powered, the system came to 4.99 +/- 0.01 volts. Think about that: this is 50 plus year old equipment which had been in storage for decades, and it was running within 0.20% of the original specification! "

    DrG12:09 PM
    That is a m a z i n g !

    @curiousmarc , if I had a teletype in my garage I'd...

    Read more »

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