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About ChrisCrawford

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    Combat Commando

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  1. Wizard was spec'd as a 2K game, but just four months later, when it was ready, the marketing people had decided that everything should be 4K, so they asked me if I could expand it to 4K. To be honest, I really didn't want to work on the 2600 -- I was eager to get going on the 800. So I told them that you don't just expand a 2K game to 4K: you start from scratch and design it for 4K from the ground up. That was true, and marketing lost interest, so I got to move to the 800. As to the cassette problem with Scram, the first thing to try is to carefully clean the tape head with a Q-tip soaked in alcohol. Wipe vigorously; you can't hurt the head with a Q-tip. Then give it lots of time for every molecule of alcohol to evaporate away, then try to load the cassette. Another possibility is to try again with a new recorder. If you ever do get it loaded, then SAVE it to a new tape!!!! If everything else fails, there's one last desperate trick you can use: freeze the tape. Wrap it tightly in a zip-lock bag, make sure that there's no extra air inside. Stick it in the deep freeze and give it overnight to come to temperature. When it's good and cold, pop it out of the fridge, shove it into the cassette player, and load immediately. You may well damage the tape if it sticks to itself. But with some luck, it might just load. This crazy stunt actually worked for me several times. But this is definitely a Do-or-Die solution.
  2. Yes, what I call "the Mayan algorithm" looks to be a variation on Bresenham's. Again, I am surprised that nobody at Atari seemed to be aware of it, as we had some really top-notch graphics people there. It's starting to look as if I DEFINITELY didn't ask the right people! 😁 By the way, I developed that algorithm for my 2600 game Wizard, which was never published but is now bouncing around the Net. And it does correctly draw lines at arbitrary angles, and even detects blocking objects. All in a few hundred bytes of code.
  3. Thanks for clearing that up for me. I recall asking various programmers at Atari but nobody seemed to be aware of that algorithm back in 1979. Odd. Maybe I just asked the wrong people.
  4. Here's something I wish we had known forty years ago: there's an algorithm known as "Egyptian division" that executes integer division using nothing but addition and doubling. This can be executed on a 6502, and would have opened up all sorts of possibilities. There were, of course, floating point packages available for the 6502, but they ate up a lot of cycles, whereas this algorithm is really fast. I'm willing to write up an explanation of the algorithm to go along with an explanation of my old "Mayan line drawing" algorithm. I'd like to know if the Egyptian division algorithm is already well known among 6502 enthusiasts. What say you?
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