thewonderidiot

7 ms·

1.
by thewonderidiot 6mo ago
Mike Stewart here! I led the restoration of the AGC documented on CuriousMarc's channel and co-administrate VirtualAGC. There is a lot to unpack here. First: this is indeed a real bug in the AGC software. However, it did not go unnotic
2.
by thewonderidiot 2y ago
For the communications project specifically (and also a couple of other projects we have going on), I combined the FPGA AGC and the Monitor into a single design that runs on a Digilent Cmod A7-35T: https://github.com/thewond
3.
Core Rope Memory Visualizer(apolloguidance.computer)
1 points by thewonderidiot 5y ago|0 comments
4.
by thewonderidiot 5y ago
The Command Module system test code Sundial includes a slightly earlier version of these same routines: https://github.com/thewonderidiot/sundiale/blob/master/sundi... This is a work-in-progress disassem
5.
by thewonderidiot 7y ago
No, it's not. The 1 here is using interpretive index register X1 to index onto GAINBRAK. The star on the DMP means that multiplication is indexed. GAINBRAK is one of the pad-loaded descent targeting parameters; the index selects the ap
6.
by thewonderidiot 7y ago
People frequently seem to think this is about the line number it's on (666), but that doesn't have anything to do with it. That line number is a totally modern construction; the original source code was on punch cards. That partic
7.
by thewonderidiot 7y ago
That call to STOPRATE was there to zero out attitude rate commands at the moment the astronaut switches into the semimanual final descent program P66. It was removed in the final few revisions before the first, unflown release of the Apollo
8.
by thewonderidiot 7y ago
These files were originally put on GitHub in the VirtualAGC repository [1] in 2015. The code was publicly released and digitized into these source files in 2009, through cooperation with the MIT Museum. [1] https://github.com&#x2
9.
by thewonderidiot 7y ago
Wherever we added modern comments, they are denoted by a double hashtag (##) at the beginning of the line. Everything else, minus formatting concerns, is directly from the original listing. You can see the scans we transcribed this from her
10.
by thewonderidiot 7y ago
Don is still around, and is still awesome! His memory for events around that time is surprisingly sharp, for it being 50 years ago. He's been an invaluable resource for us at the VirtualAGC project [1]. He provided over half (!) of the
11.
by thewonderidiot 7y ago
The Interpreter was written by Charley Muntz, not Margaret. Margaret wrote a large chunk of the DSKY display routines and a lot of the alarm/abort logic.
12.
by thewonderidiot 7y ago
Nah, they put a couple of precautions in to make sure you couldn't put the computer into standby accidentally. First, software has to set a bit to enable standby mode to be entered. For the astronauts, this was keying in VERB 37 ENTER
13.
by thewonderidiot 7y ago
Many years now of research and simulation of the system (I led the restoration of the computer mentioned in the article). There's not a single place where you can read everything, unfortunately, aside from the comment above. We're
14.
by thewonderidiot 7y ago
Solder is used extensively in satellites nowadays. The catch, though, is that you must use leaded solder, because the lead dramatically decreases the occurrence of tin whiskers. RoHS has been rather annoying in the aerospace industry, bec
15.
by thewonderidiot 7y ago
Did it use wet tantalums, though? If the alternative is "solid tantalums", then it didn't -- SCD 1006755, the only type of tantalum used in the computer, specifies them as "Capacitor Fixed, Electrolytic, Solid Tantalum&q
16.
by thewonderidiot 7y ago
Sadly most of what you read by googling these problems is misinformation. It was actually an incredibly sinister systems integration bug, that wasn't well described even at the time. It wasn't a switch misconfiguration; the Apollo
17.
by thewonderidiot 7y ago
To the contrary! In our AGC, all of the capacitors not tucked into cordwood holes sport a KEMET logo and part number: https://photos.app.goo.gl/oGsrgXBpNMccmkWV7 I think the Computer History Museum's might have Sprague
18.
Apollo AGC Restoration Part 1(youtube.com)
3 points by thewonderidiot 8y ago|0 comments
19.
by thewonderidiot 8y ago
Yeah, it was absolutely incredible to see that clock being generated for the first time. That was the first module we powered up, since it's the easiest -- just give it 4V and 14V power inputs, and it should start clocking. But it was
20.
by thewonderidiot 8y ago
Yes, the current plan is to do a bit of an exhibition/tour with it. Details are still murky, since we still have a good bit of work to do to get it fully working.
21.
by thewonderidiot 8y ago
Yeah, definitely. We took a ton of pictures and video. I'm not sure when they will be posted, since I'm sure there's a lot of editing to do.
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by thewonderidiot 8y ago
Hey all, Mike here! I'll be more than happy to answer any questions about the project, the AGC we're restoring, or anything else!
23.
by thewonderidiot 8y ago
I haven't used or prepared rope memory, but I have done quite a bit of research and planning to potentially construct some in the future. Using it wasn't terribly exciting; the rope memory for a program was broken up into six rope
24.
by thewonderidiot 10y ago
Indeed! He has a fun anecdote on his website [1] about the throttle control routines, which he was responsible for. His account of it is worth reading, but long story short: The ICD for the descent engine specified that its throttle respons
25.
by thewonderidiot 10y ago
Yep, that's right -- Don was the guy who came up with that procedure.
26.
by thewonderidiot 10y ago
If I recall correctly, over the course of the program some 300-400 people wrote code for the AGC, so it's not surprising that not everybody gets mentioned. Don Eyles (who saved Apollo 14) has an MIT org chart from the time of Apollo 11
27.
by thewonderidiot 12y ago
They do! They're in EXECUTIVE.agc (search for OCT 1201 and OCT 1202). Those error codes mean "No VAC Areas" and "No Core Sets", respectively. Core sets were the basic task control blocks, including each task's