The Apollo 11 Guidance Computer

wiredog writes "Dr. Dobbs has an article on the Apollo Guidance Computer with a jpg of a source code listing. Some specs: 70-lb box , Approximately 20 instructions, 16 bit word, ROM (rope core) 36K words; RAM (core) 2K words, Basic machine cycle: 2.048 MHz"

Comments

Apollo Guidance Computer Manual

[dbremner]

A Google search found this site. It lists all the commands and has an ASCII drawing of the display.

Use of GOTO?!?

[2ndPersonShooter]

I figured these NASA guys are crack engineers, so if I look at the code I might learn a thing or two. But then there it is, plain as day, the use of GOTO in line 470! I mean, come on, using GOTO in a guidance system? I couldn't believe my eyes!

470 on BLASTOFF goto MOON

Who do these guys think they are? Every 1st year CS student knows that GOTO is considered harmful.

Let's do ourselves all a favor and never go to the moon again using a GOTO statement!

By comparison...

[Gordonjcp]

The fuel injection controller in most newish cars uses an embedded controller, usually with about 8k of ROM (most of which is lookup tables) and 256 bytes of RAM.
They are usually based on 8032 family processors, and are clocked at a stunning 12MHz.
Of course, I'm speaking for the Bosch Jetronic family, newer ones are more powerful (but not by much).

But it worked

[sharkticon]

Considering that today people seem to want to throw the latest technologies at every tiny little problem they encounter the fact that the Apollo 11 worked is a testament to the fact that more is not always better, and that complexity brings its own problems.

Unfortunately, it seems as though people have gotten used to the idea that they require the latest technology, the latest "innovations" in order to be successful and cool. Hence the market for shoddy products that are rushed out quickly to customers, who can be guaranteed to solve their problems by getting the next release because it's newer and therefore superior.

Whereas this machine, so simple compared to even the simplest of embedded processors today, did what it was supposed to, and did it well. Today, we see all kinds of computer problems due to technology being thrown at projects as a miracle cure without considering what is actually required! Just look at the Navy's debacle with NT for a prime example.

Well done /. We need more stories to remind us that more technology isn't always good. Remember, 90% of everything is crap, and technology is no exception.

Complexity Kills

[Bonker]

Part of the beauty of this old, seemingly useless system was that it was simply designed, and almost perfectly optimized for the task.

Now we have astronauts taking laptops into space and using MS software for email and networking while on board. The testing cycles for all this software is long because all faults have to be eliminated, but the simple fact remains that computer and software designs are becoming so complex that in the very near future, if not already, they are too complex for use in the space program.

Hunting down a bug in a 100000 lines of code is one thing. Hunting down a bug and all the other bugs it causes in 4 million lines? NASA has already faced this problem, because they use Win 95 laptops. How about 10 million lines. How about 20 M?

What about the computer processors that run the space shuttles. Frankly, they're all old technology, because upgrading to the newer stuff is just too damned dangerous. If the video processor that powers your HUD guidance systems crashes because of an obscure hardware bug that occurs only in freefall, you're screwed.

Personally, I think that this sort of complexity is going to become the limiting factor in the advancement of technology. A point will come in the very near future when systems, be they processors or OS's, become so complex that the testing time necessary for critical use makes rapid development unprofitable.

The DSKY Rules!

[QuantumHack]

The Display/Keyboard interface (DSKY, pronounced 'diskey') to the Guidance/Nav computer (GNC) was a superb interface. I know an engineer who actually got to play with one. In a pre-GUI, pre-command-line age, the verb-noun interface was actually very intuitive. It's kind of like having a hardware interface that allows you to call various API methods or functions, which prompts you as to the various parameters, then displays the returned values.

To the astronauts, the DSKY was the GNC; the GNC really was just a box stowed in the Lower Equipment Bay.

The interface was so good, it was subsequently used on the F-8 fighter prototype. For more on the DSKY, see:

http://www.dfrc.nasa.gov/gallery/photo/F-8DFBW/HTM L/EC96-43408-1.html

To see it in action, watch the "From the Earth to the Moon" series from HBO. Most local video stores have 'em. The Apollo 12 one was my favorite for seeing the DSKY in action, when Al Sheppard helped upload new code (IN FLIGHT) to ignore a flakey ABORT button.

Best to ya,

Quantum Hack

http://www.hamhud.net

Re:Midgets are better in space

[Sethb]

Why not send dwarves/midgets? They're even smaller! You could build smaller vehicles, smaller spacesuits, pack less food, etc.

Send Mini-Me to Mars!
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