Atari arcade game source code + coinop tools

ieure

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About three years back, the source code for many Atari arcade games was made public on github.com/historicalsource. I believe these were rescued off the material atariscott donated to ICHEG/Museum of Play, but I'm not certain of the provenance. There's some really interesting stuff in there (like this signature analysis test ROM for Space Duel, and this very complete document which explains Centipede's self-test), just a ton of material, covering the mid-70s (Fire Truck, Super Bug, Subs, Orbit) up to around 1982 (Black Widow, Fast Freddy, Crystal Castles). There's also a lot of non-Atari stuff in there, mostly home computer games, but some 7800 game source as well.

The Atari arcade games are kind of a mixed bag. In particular, some of the Space Duel stuff seems to be corrupt — the project documentation and commandlists to build the ROM images contain fragments of source code, and it wouldn't surprise me if some of the game code was horked as well. Asteroids Deluxe seems to be missing the rev 2 source, which sucks! I always wanted to see exactly what they changed about the difficulty level. But still: interesting stuff, especially if you're a boring old dweeb like me. None of this was terribly useful, because Atari wrote their own macro assembler, linker, and image splitter (MAC65, LINKM, and IMGFIL), which all this stuff uses. No other assembler can handle these files, and everything makes extensive use of the macro facilities — especially the vector games. So it seemed this was all little more than historical curiosity.

Until... around a month ago, copies of the tools used in Atari coin-op also surfaced; I'm not sure where from. IMGFIL is still missing, but is the simplest of the tools, and can be replaced with some trivial Unix dd commands. And the person who released those was able to use those tools in a PDP-11 emulator to assemble a bit-exact copy of the Centipede v4 ROM images, for the first time in 40+ years.

For the less programming-oriented dorks around here, what this means is that anyone can now have, more or less, the same ability Atari did to revise these games, and make more like them, if they want. This has always been possible, but now it's significantly easier. I'm excited to see what comes of this!
 
I ran into the exact same problem with Sinistar and Joust, as both games uses an outdated assembler that's currently lost software. Fortunately, I found a newer program called Macroassembler {AS} that uses similar-enough syntax and supports a lot of different kinds of macros (finding an assembler that properly supports them was mandatory as Sinistar's source code heavily relies on them). I ran some tests and after getting used to the crazy manual for {AS}, I was able to re-target the source code for both games and build a perfect ROM set copy for each one.


After the Joust rewrite, I looked into the source codebases for Centipede and Crystal Castles, to see if it was possible to retarget them for {AS} as well but the source code syntax is pretty different. Like you said, some of the code appears to be incomplete. I tried looking through Quiz Show since that's the first game to use the famous pixel font sprites that everyone uses, but unless I missed something, I couldn't find them. Other games like Dig Dug are just a dump of the ROM images, and a print out of the ROM filenames with the name of the programmer at Atari who got them ready for production.

I know that MAC65 was later ported to Atari computers but I haven't done enough research to see if it could handle the coin-op code...I will say that the code examples that I've seen in the MAC65 manuals and what's in the historicalsource codebases do look similar though.

{AS} also comes with a program calle P2BIN that I used to split the binary data into the final ROM images. I think it's possible to port this Atari code over to {AS}, but it will just take a lot more time and effort (quite possibly even more so than the Williams games). Meanwhile, this is really awesome that the Atari dev tools themselves have been recovered and since the code hasn't been rewritten, you're essentially building the code the exact same way they did at Atari HQ, forty years ago. Thank you so much for sharing this news!
 
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