There's a fascinating guide, http://pdf.textfiles.com/technical/2600_guide.pdf http://pdf.textfiles.com/technical/2600_guide.pdf In short, the TIA chip does ac

There's a fascinating guide, http://pdf.textfiles.com/technical/2600_guide.pdf http://pdf.textfiles.com/technical/2600_guide.pdf In short, the TIA chip does act as video memory - but not the way we treat it today. It has various registers that you can write into to define how the next line will be drawn. eg, you create a background by writing 20 bits into the 'playfield' register. This is mirrored vertically to fill out a 40-bit wide background, and then you write in a foreground & background colour. Similar registers exist to hold sprites for a ball, two players, and two missiles. And then if all of this didn't seem limiting enough for you, your game (the only process running on the machine) is responsible for maintaining most the timing for the television controller itself - so you actually spend most your time managing the TIA, with only a small number of cycles at the end of each line, and a better number of cycles after the last line, but before the next screen starts drawing - in order to actually perform game logic itself.