Apollo Guidance Computer Part 14: Bringing up fixed rope memory

We bring up the first memory section, fixed core rope memory. This is the "ROM" that holds the programs. Although based on ferrite cores, this is read-only and very different from the erasable core memory. Our AGC actually did not come with flight rope modules, but instead with a pair of Raytheon boxes used during development for simulating the final ropes. Unfortunately these boxes are undocumented and of much lesser build quality than the flight hardware, which should keep us on our toes. Thanks to our sponsors Samtec for the connector pins and PCBway for the monitor PCB: www.pcbway.com
Full video of Mike's explanation here:
• Apollo Guidance Comput...
Some relevant links:
Playlist of the restoration series: • Apollo Guidance Comput...
Block I AGC period documentary: • MIT Science Reporter-"...
Inertial navigation system documentary: • Video
Schematics: www.ibiblio.org/apollo/links....
and: archive.org/details/agc_handb...
Mike's AGC backplane viewer: apolloguidance.computer/200310...
AGC software repo: github.com/virtualagc/virtualagc
The Ultimate Apollo Guidance Computer Talk: • 34C3 - The Ultimate A...

[@CuriousMarc]

Mike's long explanation is available in full in this bonus material video here: kzbin.info/www/bejne/hH_PmH1rZ9yofac

[@TheBitKrieger]

CuriousMarc Thanks!

[@hinzster]

7:53 (a short and an open pin) "You'd think they canceled out." - That is top electronics humour just there :P

[@cameron1975williams]

Two weeks to go until the 50th anniversary of Apollo 11. Great work guys :)

[@zeeclone]

Right. Monday. Let's get started work after a long weekend of children's birthday party. Motivated and ready. No distractions. Ooo! Another CuriousMarc AGC video!

[@larryscott3982]

I had no idea just how thoroughly and meticulously, or difficult and lengthy this project is and has become. This is 100s of thousands of dollars of combined effort, skill, resource, and time. Pure unadulterated mutual love and concerted effort. I hope this AGC restoration gets the public acknowledgement that it deserves. It goes to show that the Apollo project was an effort rivaling any of 7 wonders of the world. I would be interested to see a comparison to the Russian technology of the same period.

[@NicolajTopp]

Well said!!

[@larryscott3982]

Nicolaj Baramsky There’s several documentaries on the design and building of the AGC, filmed on location during the fabrication. I’d like to this in parallel and a combined montage.

[@johnclawed]

Russian technology of the period was a music box with switches controlled by cams on a rotating drum. That's how our astronauts described it after seeing it aboard Soyuz in the Apollo-Soyuz mission in 1975.

[@bborkzilla]

I was four years old when Apollo 11 happened. I remember running outside that night to look at the moon and see if I could catch a glimpse of the astronauts as they did their thing. I finally met Armstrong a few years before he died - he was one of my heroes and one of the reasons I got into engineering in the first place!

[@lexihaley2887]

Also - this entire team is so cool! Can y'all do a group photo at some point - maybe a round of brief (re)introductions as to who everyone is? Thanks again for making these videos; really really excellent!

[@damientonkin]

So the fixed core rope memory is now fixed fixed core rope memory?

[@lwilton]

Its actually fixed variable core rope memory since it is a simulator. :-)

[@CuriousMarc]

The curiously named fixed fixed memory refers to page 0 in fixed memory (indeed from core rope) that does not need to be moved into view within the very restricted address space of the AGC by using the memory bank register (which is all the other pages, or the majority of fixed memory). Hence it’s doubly fixed. It would have been better named base bank or base page fixed memory, but it’s much less fun.

[@poulx]

It would be very interesting to see the explanation in a separate video. It's kind of besides the whole point to skip it. Thank you for your very, very exiting videoes. Such a team! Best regards,

[@FoxCutter]

Yeah, I'm really into that stuff and would love to see the full version.

[@tedvanmatje]

I agree.....totally....in less than a heartbeat :)

[@lwilton]

Nice work! BTW, if you punch the "scope" button on the 7854 after it powers up it will clear the "self test complete" message on the screen.

[@michaelriley1118]

As a computer engineer, I've always appreciated the AGC. I am very glad you guys are working on one and sharing your experience with us. I also appreciate the very technical information as well.

[@yorgle]

One of my favorite parts of my week! "Two days of debugging, two capacitors is the solution". Sounds about right! :D

[@HenrikDanielsson]

"A capacitor a day keeps the transients away" :D

[@ChestonU]

I love watching this kind of Digital Archaeology, because that's what this is. Digging into our past through empirical observation, analysis of known information, and re-learning things that have long been forgotten. Totally love the direction this channel has been going. You guys are true specialists, and its awesome that someone is taking the time to preserve and resurrect such important parts of our history - so that we can continue to learn from it and avoid repeating past mistakes. Cheers.

[@Blowcrafter]

you should have left that long explanation part in the video (maybe moved to the end). I would have wanted to see it :)

[@Tedd755]

Put it on CuriousMarcTwo. Or should it be 2Curious2Marc - Tokyo Drift?

[@sheep1ewe]

I absolute agree, i wanted to hear that too.

[@heatshield]

I would like to see that sometime, too.

[@dolphinclassical]

I too would love to see those 11 minutes of explanation. This is a tech channel after all! S’il vous plaît.

[@userPrehistoricman]

If it really was 11 minutes, some of it is missing from this video. The sped up section was only 4 minutes ish in real time.

[@gusbert]

Ha! In England if you call someone a "dipstick" it means they are stupid, an idiot! Keep up the fantastic videos.

[@CuriousMarc]

We confirm. Dipsticks are stupid.

[@djmips]

I'm pretty sure that's American slang originally...

[@toboterxp8155]

Can we get the eleven minute in depth explanation as a seperate video?

[@littlejason99]

Yes, we want the extended cut!

[@userPrehistoricman]

You can slow it down 20x and get a slightly legible result.

[@Strothy2]

your wishes just got granted!

[@shifter65]

Whoa, seems like Mike has completely memorized/understood every nook and cranny of the AGC circuitry.

[@nrdesign1991]

The amazing thing is not the AGC itself, but all the engineering and work that went into creating it, double that, they had only the technology of the 1960s at hand!

[@michalsvojanovsky8025]

That memory is CRAZY, I can`t imagine how it could be so reliable :o

[@Tedd755]

This is a wonderfully fascinating series. Not only your hard work getting the AGC working again, but your video documentation is top notch!

[@Cougar333]

I'm obsessed with this series. I'm on the edge of my butt for every new video. Incredible work fellas!

[@Zerbey]

You guys are amazing, good luck and I really hope you can get this up and running in time for the anniversary!

[@alpcns]

Spectacular. And a pleasure to watch. You guys are absolutely brilliant.

[@glenwoofit]

I get excited to watch what you guys get up to with this project, What an incredible job you're doing. Thanks for these videos.... I can't wait till the next one.

[@rosswaring2835]

This entire process and your dedication to it is breathtaking. Great work guys!

[@jeffkahn6852]

Watching you guys problem solve is such a gratifying experience! Thank you for sharing your creativity craft and methods.

[@NicolajTopp]

Man, I love this series! And you guys are so clever! I couldn’t have done this kind of debugging in my life ... I admire your thinking capabilities!

[@dr.strangelove5622]

Wonderful video as always. You guys can do it!!! This the most beautiful and exciting series on KZbin for me.

[@BigMouth380cal]

Without a doubt, you guys exemplify the Apollo Program spirit.

[@WellingtonIronman]

I know so little about how computers actually work, yet I fund these videos accessible and easy to understand. The passion shown by the experts, their incredible knowledge, the ability to trouble shoot problems. Fascinating viewing. Thank you very much

[@chevon5707]

Amazing perseverance and problem-solving on display - I’m enjoying this series so much!

[@unlokia]

Marc, your channel is absolutely behind compare, you have no equal peers online, with such unpretentious, hardcore, unique and EXTREMELY interesting videos with VERY hard to come by machines and friends with in depth knowledge of them. Wow! God bless you and thank you so much. Matthew.

[@RiccardoMacri]

Finally, people using the word "glitch" when its appropriate.

[@wayneholder]

I love you guys! So fascinating to watch this play out.

[@timcurran7841]

Can’t say it enough! You guys rock! Thanks again, looking forward to the next installment!

[@stuartharper2289]

I understand maybe less than 1% of what you guys are doing but I’m completely hooked on this mini series. Good job guys and great content

[@skaaltel]

Any time I start to feel too smart I just sit down and watch one of these videos. I know a little bit about consumer computer repair, but this is well above my pay grade! Thanks for taking the time to lay a little knowledge and understanding on me. It's kind of like visiting a museum and getting a personal guided tour.

[@rsyoung01]

Hardcore debug, analog and digital... 10 x Thumbs Up!

[@givemeakawasaki]

Nice Debugging Guys! awesome to see all the old test units at play with newer tools to give the information needed to fix the problem! Excellent work!

[@jonnychooch6624]

Just WoW, very much a time swallowing monster,, impressive for sure,, keep up the amazing dedication

[@leandrolaporta2196]

I just now found this, amazing what you guys have done, Mike's abilities don't cease to amaze me, this guy is a machine!, Man I I'm a hardware engineer and been working on assembler and digital circuits most of my life and after seeing what Mike and all of you are doing here I feel like a moron, fantastic series, thank you so much for done that, too bad I was so late to the party

[@skfalpink123]

Another outstanding episode, of what has to be. the best thing on KZbin. P.S. I just ordered the T-Shirt

[@FightAtTheForum]

These are the fabled men in sheds that overcome obstacles..

[@flymario8046]

Its so glorious! you guys are doing some great work!

[@antoninbesse795]

These videos are like catnip - I cant resist them. Why do I find them so good? Why?

[@brentgoeller8257]

This series is so awsome. I dream of working on something like this. God bless you guys.

[@campbellmorrison8540]

Wow guys I love it, kept up with most stuff until now but the rope memory is definitely a struggle for me. Reminds me of a bunch of my friends huddled around an 8080 development board trying to get some interface working. Wonderful to see real fundamental knowledge ( and old test gear ) at work

[@marct3928]

Great work guys! Can't wait to see the next episode.

[@KJ7BZC]

Great work as always, I would love to see this working soon. Keep it up.

[@JBFromOZ]

Totally awesome work guys! Smashing it out of the park!

[@scowell]

Ken is a beast! Way to go guys... I hope to see this system working someday.

[@BlackEpyon]

I still have to argue with people who think that we didn't have enough computer power to get to the moon. I point them to this playlist.

[@TheRealColBosch]

I never thought the Apollo missions were faked, and these videos - beyond being totally awesome in their own right - are definitely confirmation. There is no way anyone would've gone to this much trouble just to shoot the whole thing on a soundstage. The point of fraud is to save time, effort, and money, after all.

[@BlackEpyon]

@@reallyme3573 When you say, "A modern day phone with 8GB of data," you're talking about your data plan limit. What you MEAN to say, is storage space. which just means that your modern phone could fly to the moon and have plenty of room left over. Not a lot of calculations are needed, they used to do them on slide rulers, which takes a lot longer. Only a couple decades earlier, in the Manhattan Project, they were computing much more complicated equations using mechanical calculating machines larger than a typewriter before they got access to an IBM mainframe. Core memory actually was pretty fast for the 1960's compared to other forms of memory, it was just limited by the speed of the TTL logic. It was a 2MHz 16-bit computer, which is comparable to the first generation of home PCs only a decade later. I've still got a computer that isn't much faster, still doesn't have a math co-processor, and it does fractions just fine. You don't need a math co-processor to do fractions, and you never did. You just tell it to stop counting after so many decimal points, so it doesn't fill up the registers. Each sequence of the journey was pre-programmed into the ROM, and when you're programming in assembler, there's no bloat to worry about, so not much space is actually needed. It's been uploaded to GitHub, if you want to go over it: github.com/chrislgarry/Apollo-11/tree/master/Luminary099

[@markwilliams-ko5zq]

@@reallyme3573 the real problem is that so few people actually know how to write efficient code at the machine level these days (these guys still do),

[@SimonRousseau1]

For me this is building up more hype than the game of thrones finale did. Even at 36 this is making me want to get into more electronics stuff. Thanks a ton.

[@dufflepod]

Wonderful work!

[@twobob]

Definitely got one of the tougher meals to chew on. Much respect to that man.

[@BilisNegra]

6:45 I'm so glad even you recognise understanding some parts in your videos can be challenging. I've followed the whole AGC series without any serious, in-depth computing knowledge at all, go figure my struggle at some points (though not as many as I expected at first). So finally I'm not feeling like the only idiot watching this, yay!

[@RobotnikPlays]

Ken's a funny guy! Well done to all involved, keep it up!

[@chriholt]

Just awesome. Can’t wait for the next episode!

[@shyleshsrinivasan5092]

Very grateful to you for these videos !

[@rallokkcaz]

God I love this stuff, we all take computers for granted now a days. This is what some of the most impressive engineering I've ever seen.

[@andrewwong2000]

Some really outstanding (reverse) software & electronics engineering !!

[@asgerms]

I love how a Xerox Alto is just sitting there on a desk in the background while they work on an Apollo AGC. Paradise for geeks :)

[@LiquidCheney]

Ken is a national treasure.

[@ShaunOvertonNZL]

The anticipation.... Can't wait to see more!

[@andie_pants]

4:12 Ken, you are the MAN!

[@cda32]

These videos should have a million views

[@rogermason1674]

I'm right there with you guys in spirit sending you positive thoughts...to quote Oddball (Donald Sutherland) from Kelley's Heroes " Crazy... I mean like, so many positive waves... maybe we can't lose, you're on!"

[@DavidStahlOLDHAPPyMACs]

Great Job Terry You Do Fine Work

[@michaelcherry8952]

All this time I thought Apollo 11 used a Saturn V rocket to get into space and it turns out they were using rope! The things you learn on KZbin.... Any chance of a collaboration with a channel building a full-size Saturn V? :-) This is one of my favourite KZbin channels. Keep up the good work!

[@nmccw3245]

Great job gentlemen. Thanks!

[@soniclab-cnc]

This has been such an amazing series of videos. Looking forward to the next episode. Thank you guys so much.

[@SomeGuyInSandy]

Masterful troubleshooting!

[@mymessylab]

Hey Gentlemen, that it’s magic So enjoyble clips. 👏👏

[@markm0000]

This project is beautiful

[@TheMrMinecrafttnt]

I follow this project from the beginnig and i love it!

[@GameTechRefuge]

Great stuff. Really enjoying this series. The DS1054 scope seems really popular, shame it's so hard to find, been looking out for one for some time now.

[@afloyd4976]

Exciting work going on!

[@gyrcom]

The very best the internet has to offer! I am Gobsmacked!

[@DEVAXTATOR-1]

Thank you for your hard work

[@Maxxarcade]

It still blows my mind how physically difficult it was to make memory and other parts back then. It just goes to show how devoted people were to projects. Stuff got done, even if it had to be invented on the spot. And it's great to see a group of people that carry on this type of work.

[@markwilliams-ko5zq]

same story with the F1 main engines on the Saturn 5, while the blueprints still exist, a whole lot of custom fitting had to be done by hand to actually make them work, and the notes on what was done there either was never written down, or lost. the team that looked up possibly recreating those engines actually found it easier to come up with a simplified cad model that brought the original engine's some 5000 parts down to about 55-60 pieces . simply because modern design and manufacturing techniques allow us to build parts with shapes and complexities that simply weren't remotely possible then

[@freddyburger5574]

The saga continues!! So exciting! Can we please have the 11 minute explanation in its own video? I'm curious about the fault and would like to know what he said... remember, we're nerds too!

[@teckeleddie]

Well done guys. It is way above my head, though I do like flashing lights, lol.

[@edgeeffect]

A Mitutoyo rule for the Americans and a More and Wright Rule for the rest of us... now that IS pure quality!!! It'd be great to see a special edition with the "11 minute explanation" left in for the uber-nerds in the audience. ....... ah back in the days when "plug-ins" really did plug-in!

[@MatthijsvanDuin]

Nice application of the BeagleBone! PRU is awesome

[@mikestewart8928]

Agreed, I love the PRUs. Their crazy little assembly language is one of my favorite's I've used.

[@MatthijsvanDuin]

@@mikestewart8928 It's very nice and clean indeed. The only thing I don't like is the libprussdrv library on the linux side, which is part of why I created py-uio[1], and hopefully one day I'll get around to also make a better C/C++ library. [1] github.com/mvduin/py-uio

[@pmcgee003]

That's some super debugging right there. Huzzah!

[@CassetteMaster]

This is amazing!!

[@shifter65]

Talk about a dream team!

[@tekvax01]

Marc!! Please, can you also publish the fast-forwarded talking complex bits too, in another video?! I'd really like to hear all of it!! p-l-e-a-s-e-e-e!!

[@CuriousMarc]

Published now, next video kzbin.info/www/bejne/hH_PmH1rZ9yofac

[@macpb2892]

Vous êtes génial!

[@doc_sav]

Ken must have vast amounts of patience. He had a tough task in that box.

[@DanielRowe]

Just awesome

[@dustysparks]

New T-Shirt Idea: Marc & Ken & Carl & Mike

[@brianbak6405]

I am not on Jedi level with eanything you guys do here.! I have som basic knowledge of some stuff. I am absolutely fascinated with all of this 👀.! I just want more .!!!

[@matthewmiller6068]

Any chance that you can post the normal-speed version of the "11 minutes of explanation rope memory addressing is complicated"? I really enjoyed your "episode 4-1/2" with the technical details...some of this stuff really takes me back to cool stuff of building a simple computer (albeit simulated) in college out of individual gates - I'd love to hear all the nitty gritty about how the Apollo computers address memory!

[@CuriousMarc]

Posted here kzbin.info/www/bejne/hH_PmH1rZ9yofac

[@killemtoenjoythesilence]

I truly feel stupid watching these videos. I understand the basics of how these things work but wow this is incredibly complicated.

[@adrianobueno6984]

Amazing series of vídeos, thank you for taking your time to film and share everything. It's so nice to see the AGC running again! BUT I'm struggling really bad to understand how the Apollo's rope memory was woven, are there address and data lines? Are there data lines? How they are read? I understand how Univac rope memory works, no problem, but AGC is completely different ball game since it runs using it's rope memory (and not using it just to start or load the system to the RAM). Hard to me to figure-out how the system address it and read the data.

[@CuriousMarc]

If you thought core memory was complicated, wait until you see core rope. Yes it has data and address lines, but used completely differently. Ken has written the only comprehensible article out there explaining this: www.righto.com/2019/07/software-woven-into-wire-core-rope-and.html

[@adrianobueno6984]

@@CuriousMarc Great, thank you! Looks like address lines (inhibit?) are really tricky...

[@adrianobueno6984]

@@CuriousMarc I agree, It's a really nice article indeed but what I can´t understand is that in the Fig 3-12 we have an example with 4 cores, 4 inhibt lines and 16 sense ones (only sense 1, 2 and 16 are shown), how can sense lines 2 and 16, that goes exactly through to the same cores, get different results in the truth table? From the example in that figure, core #2 is active. From truth table, if core #2 is activated the results are: sense 2 = 1 and sense 16 = 0, but they use the same cores! how come opposite results? Please what I’m missing?

[@SuperAWaC]

i was going to ask this on a previous video but forgot- what was that small vacuum you were using to try and clean out the plug? i've been looking for a good small vacuum like that for years.

[@zaphhood4745]

Nice!

[@neilolif]

Watching you guys work your magic makes me ling for the "good old days" of debugging development hardware at IBM for "MASSIVE" 1.6 megabyte hard drives.., (Not!!!)

[@MattVileta]

Love it