The Amiga could do a lot more than the Atari with the gfx chip. The Atari had three modes, 320x200, 640x200 and 640x400 so two horizontal and two vertical resol

The Amiga could do a lot more than the Atari with the gfx chip. The Atari had three modes, 320x200, 640x200 and 640x400 so two horizontal and two vertical resolutions. It also can change frequency between 50 and 60 Hz but that wasn't instant, it took a couple of frames to stabilize. This I think you could use to get borderless screens with even higher resolution but I've forgotten exactly how it worked. For the highest resolution you needed a better monitor though so I didn't have much experience with that one. The Atari Falcon also had more resolutions with instant switch but my memory is getting quite fuzzy there :-)