The 2600 had a 1D display buffer. You would rewrite the contents of that buffer at the end of every scanline to actually get a 2D image. Game logic would usuall

The 2600 had a 1D display buffer. You would rewrite the contents of that buffer at the end of every scanline to actually get a 2D image. Game logic would usually only run during flyback. (Yes, that's why atari chess did not show the board while thinking, and why if there was a bug you'd get a 1D horizontal image all over the screen)