
Software of the Apollo guidance computer was hand-woven into rope core memory - raldi
https://www.youtube.com/watch?v=P12r8DKHsak&t=20s
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ErsatzVerkehr
I thought this was interesting (both that the space shuttle still used core
memory, and that the challenger memory was retrieved and its contents
recovered):

> Core memory is non-volatile storage—it can retain its contents indefinitely
> without power. It is also relatively unaffected by EMP and radiation. ...
> For example, the Space Shuttle flight computers initially used core memory,
> which preserved the contents of memory even through the Challenger's
> disintegration and subsequent plunge into the sea in 1986.

(From [http://en.wikipedia.org/wiki/Magnetic-
core_memory#Physical_c...](http://en.wikipedia.org/wiki/Magnetic-
core_memory#Physical_characteristics) )

Note that this core memory is a little different than the rope core memory
described in the linked article.

~~~
adrianhoward
My dad was a draftsman, and worked on everything from conveyer belt systems to
satellite test rigs. This was in the years before CAD and he often brought A1
and A0 paper home from work for us kids to scribble on.

One time I can remember getting this sheet with this wonderful crossed-grid
with rings pattern. I remember staring at it for a good ten minutes before
turning it over and trying to draw spider-man ;-)

It was several year before I realised that I was looking at a drawing of core
store.

One of my life regrets was that I didn't know to save it. I'd love to have it
on the wall framed now ;)

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inDigiNeous
Interesting. Reminds of the Mayan Quipu system
([http://en.wikipedia.org/wiki/Quipu](http://en.wikipedia.org/wiki/Quipu)) of
storing information in knots in ropes.

I've read somewhere that they even had simple "computers" made out of stone
structures that would then have these knot systems inserted into them, but for
the life of me I can't remember what these were called.

So the Mayans did it first! ;)

~~~
abrowne
Slight correction: quipu was used in Andean South America (e.g. by the Incas),
not by the Maya in Mesoamerica.

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mx12
Here's a link to the full video:

[http://www.dailymotion.com/video/xxxiij_moon-
machines-2008-p...](http://www.dailymotion.com/video/xxxiij_moon-
machines-2008-part-3-the-navigation-computer_tech)

Around 37 minutes they talk about the alarms on approach and how the dealt
with them.

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Wingman4l7
This is from the series _Moon Machines_ , which I cannot recommend highly
enough. It's got interviews with the people who worked on Apollo hardware,
testing footage I've never seen elsewhere, and some great anecdotes as well.
It really gets down into the nitty-gritty design challenges they faced -- it's
the Apollo program as the engineers saw it, not the astronauts.

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js2
I submitted this a couple years ago but it got no traction then:

[http://history.nasa.gov/computers/Part1.html](http://history.nasa.gov/computers/Part1.html)
(Computers in Spaceflight: The NASA Experience)

Here's some details on the Apollo guidance computer:

[http://history.nasa.gov/computers/Ch2-5.html](http://history.nasa.gov/computers/Ch2-5.html)

Edit: just resubmitted -
[https://news.ycombinator.com/item?id=7657876](https://news.ycombinator.com/item?id=7657876)

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ISL
[http://en.wikipedia.org/wiki/Core_rope_memory](http://en.wikipedia.org/wiki/Core_rope_memory)

~~~
hanley
> Some programmers nicknamed the finished product LOL memory, for Little Old
> Lady memory.

The original usage of the term LOL.

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amcnett
I code at approximately the same rate as the core rope memory weavers wove. I
wouldn't trust mine to help people fly to the moon, though. That's incredible!

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lotsofmangos
Here's how to make some -
[http://www.neazoi.gr/coreROM/index.htm](http://www.neazoi.gr/coreROM/index.htm)

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fractalsea
Very interesting video. I had no idea.

It would have been interesting to see how the program was actually executed.
Do the rings around the rope core somehow create a circuit that allows the
processor to "know" in which order the 1s and 0s are in? Or is there some kind
of mechanical process?

It must have been very easy to make mistakes with all that manual work. I am
assuming the weave must have had to have been checked many times.

~~~
lazylester
I'm pretty sure the bytes are sequentially addressed, but the program (memory
contents) may contain branching, conditionals etc to load the next address.
Just like assembly language. If I recall correctly, the microprocessor logic
on these missions was RTL (resistor-transistor-logic) which was the
predecessor of TTL.

~~~
akira2501
It was sequential but bank-addressed. The AGC had it's own assembly
language[1] and was a pretty recognizable general purpose computer[2] for it's
time.

1:
[http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/a...](http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/apollo/public/archive/1689.pdf)

2:
[http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/a...](http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/apollo/public/archive/1717.pdf)

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userbinator
Using core RAM (not the ROM in the video, but similar) with an Arduino:
[http://www.corememoryshield.com/report.html](http://www.corememoryshield.com/report.html)

~~~
boobsbr
What an incredible project.

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bananas
And I thought going through the program, debug, UV erase cycle of a 2716 was
torturous!

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nevster
That's a pretty impressive build tool.

Before there was grunt, before there was maven, before there was make...

Worth including on the the
[http://en.wikipedia.org/wiki/Build_automation](http://en.wikipedia.org/wiki/Build_automation)
page?

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api_or_ipa
please tell me this was a production build and not used to backup nightly
builds.

~~~
InclinedPlane
Back then "source control" was making a copy of the physical paper copies
containing the code.

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spikels
Rope memory is quite beautiful. Seems like an alien technology - almost
organic.

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sferoze
The show that this clip is from is amazing! The Moon Machines. I highly
recommend it

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Demiurge
I wonder what word they used at that time to distinguish hardware and software
bug?

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meemo
Which television program is that from?

~~~
oskee80
That clip is from part 3 of Moon Machines:

[http://en.wikipedia.org/wiki/Moon_Machines](http://en.wikipedia.org/wiki/Moon_Machines)

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jloughry
Warning: this video automatically plays.

~~~
raldi
Just like every other YouTube link.

~~~
a3n
Unless you have Flashblock.

