Amiga Screens: A Primer Autumn 2026

Whenever something Amiga-related is mentioned, at least one Amiga fan must explain screens. Amiga screens can have different resolutions, can be dragged, and can display graphics at varying colour depths. This primer focuses on OCS (Original Chip Set), though the same basic principles apply to ECS (Enhanced Chip Set) and AGA (Advanced Graphics Architecture).

On the Amiga, a screen is an area onto which graphics are drawn. Games and demo programmers may call it a playfield or discuss raster splits, but screen is the operating system’s term. A program can open multiple screens at different resolutions, unlike the single, fixed-resolution display common today. In the CRT era, an image viewer on a VGA-capable MS-DOS machine might use a 16-colour, 720x400 text mode, then open a 256-colour, 320x200 display for an image.

The Amiga typically uses indexed palettes: limited per-screen colour registers hold values selected from a 12-bit colour space, or 24-bit on AGA. Planar graphics stores each bitplane separately; adding bitplanes increases colour depth. One bitplane gives two colour indices, two give four, and so on, up to five bitplanes and 32 colours on the original Amiga hardware, or eight bitplanes and 256 colours on AGA.

On OCS and ECS, the maximum bitplanes depend on resolution, designed for PAL or NTSC television sets. Low-res is 320x256, or 320x512 with interlace, in up to 32 colours; high-res is 640x256, or 640x512 with interlace, in up to 16 colours.