For many Generation X’ers like myself, the Atari 2600 brings back memories of many fun hours spent playing video games. We didn’t know it back then, but the 2600 was little more than a CPU, a crude video subsystem, and a sound chip bundled into a console. Atari 2600 cartridges contained a ROM chip, which had to more or less create the entire game from scratch. All the magic was done with really clever assembly-code (or even machine code) programming. It’s all described in a fascinating book called Racing The Beam.
I recently came across a neat video on YouTube where David Crane (the creator of Pitfall and the even more impressive Pitfall II) gave a talk on how the amazing effects in these games were accomplished.
The Atari 2600 was, initially, really only designed to play two games: Pong and Combat. Its hardware was built around two “player” sprites and three “missile” or “ball” sprites. Not only that, but the display was built one line at a time. The game code in the cartridge had to keep track of which line it was on and then display the line when the right time came.
It had to do all this in real time, before the beam swept across the screen again!
How did Crane and other developers convince this system to produce complex games such as Pitfall? By employing every trick in the book, and writing more than a few new ones into the margins for good measure. (Why did the background graphics in some games look weird? That was actual machine code being displayed, due to a lack of space to store bitmaps!)
Crane’s talk (including a Q&A session) is just over an hour long — but this is time well spent for anyone interested in the nuts and bolts of making computer games. These guys made magic out of almost nothing.