167 – The Apollo Guidance Computer
Guest: Frank O’Brien Host: Markus Voelter Shownoter: Stefaan Rillaert
This episode is a mix between computer architecture, programming and (historic) space flight. We cover the ins and outs of the Apollo Guidance Computer. Our guest ist Frank O’Brien, who wrote an incredibly detailed book about this machine. In the episode we cover the hardware architecture, the instruction set, the various layers (native, executive and interpreter) as well as some mission programs.
Frank O'Brien | Book 'The Apollo Guidance Computer' | PowerPoint presentation of Frank O'Brien about the AGC | Omega Tau 83 How Apollo Flew to the Moon | Omega Tau 97 How Apollo Explored the Moon
Overview hardware and software0:08:38
Apollo Guidance Computer | Mid 60s NASA/MIT documentary 'Computer for Apollo' | CPU | Computer memory | Core rope memory | 'Weaving software into core memory by hand' | History digital computers | History integrated circuits | Octal | Assembly level programming | Interpreter | Multiprogramming | Apollo Command Module | Apollo Lunar Module | Saturn Launch Vehicle Digital Computer | Apollo Abort Guidance System
Floating point | Signed number representations | Ones' complement | Two's complement | Parity bit | State vector | Memory bank | Processor register | Bit shifting | Direct memory access | Opcode | Index register | Call stack | Global variable | Interrupt | Verb and noun codes on Virtual AGC | Apollo 15 Delco LM Manual with information about DSKY and lists of verbs and nouns
Executive or Operating System1:14:37
Operating system | 'The Apollo guidance computer: Software' in 'Computers in Spaceflight: The NASA Experience' | Memory management | I/O | API | Cooperative multitasking | Preemptive multitasking | Watchdog | Core sets and Apollo 11 landing | Virtual machine (VM) | p-code | Intermediate language | Polish notation | Forth | Programmer's Manual AGC Assembly Language | Autopilot | Low-level programming language | High-level programming language
Foreground/background program | Inertial measurement unit (IMU) | Foucault's pendulum | Gyrocompassing | Gyrocompass | Abstraction level
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Thank you Mark yet another terrific talk.
I really enjoyed listening to Frank talk so passionately about this humble piece of kit.
A funny part was when Frank said he would to love to flip a switch and manually fly the Saturn booster into orbit. Maybe you were concentrating on a few things at the time but, in a non-detached way, you asked about the kind of instrumentation and Frank said it was little sheet of cardboard. Amazing. Frank then went on about how to make the best of a bad situation and you just said yep, yep. yep. No offense but it sounded like a pair of stand-up comedians. lol
I don’t even remember this! But I admit that sometimes in these longish episodes I have short periods of inattentiveness and may not catch on to funny situations :-)
Frank was great, but I found it this time hard to follow some sequences of the podcast as you were so lost into some details that required previous knowledge from the book that was not available to the listener.
Ok, thanks for the feedback. This was maybe because I did read the book in advance, and maybe because I have a background in this computer stuff. Sorry.
I just finished listening to this episode. I honestly feel like I could continue to listen for hours more. So interesting! And you get the clear feeling of how much Frank seems to love talking about it. His passion is contagious, I just ordered his book from Amazon.
Anyway, thanks and congratulations for a fantastic episode.
You’re welcome :-)
After listening to this wonderful computing history lesson, I think I can safety say during my Arduino classes that the ATMEGA328 is more powerful than the Apollo guidance computer. Today, I’m more grateful of what I have to work with. Thanks.
Yes, these old computers makes one appreciate the current stuff :-)
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Great talk…WOW…I remember those days in the beginning…These computers we huge compared to now! Good to see somebody with passion! Keep up the good work!
And now the source code got released :)
A South African man found portions of the hardware.
Unfortunately, I learned about this episode AFTER friends of mine did the “Ultimate Apollo Guidance Computer Talk” on #34c3. (https://media.ccc.de/v/34c3-9064-the_ultimate_apollo_guidance_computer_talk )
I helped preparing parts of the talk and that book of Frank O’Brien was such an important reference.. BUT OF COURSE omegatau did an Episode on AGC. What was I thinking? :D
However, thanks for doing this great podcast! I think I know what it means to maintain that frequency with content of this quality. :)