Technique · rendering

CHR RAM

Tile patterns kept in RAM on the cartridge, which the game fills from program ROM, instead of fixed tiles in CHR ROM.

stubAlso: CHR-RAM, pattern RAM, tile RAMUpdated 2026-10-23

With CHR RAM a cartridge gives the video chip writable tile memory, so the game loads its own tiles: a set per area, compressed, or changed while it runs. Writing tiles takes time the video chip allows only with the screen off or during vertical blank.

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Games

Every claim about this mechanic, by game (1)
Mega Man 2 1988Mega Man 2's _object_tiles_update is the loop Mega Man enters at _init_object_tiles, which copies the tile buffer to CHR RAM, with its RAM at new addresses. Mega Man 2 drops the test in front of it and the _object_tiles_update_yellow_devil path, which writes two bytes at each of several PPU addresses, a row ($20) apart.Code