When launched in the US, the Atari 400 & 800 came with a CTIA (Color Television Interface Adapter) chip, which offered 9 graphic and text modes (GR.0-8) in Atari BASIC and a 128-colour palette. In early 1982, CTIA was replaced by GTIA (Graphic Television Interface Adapter), which provided 3 additional graphics modes (GR.9-10-11) in Atari BASIC, with a 256-colour palette. The GTIA chip equipped all new Atari 400 & 800, and their successors.
POKEY (POt KEYboard integrated circuit) is a digital Input/Output chip. It handles such disparate tasks as the serial I/O (SIO) bus and its peripherals, audio generation, keyboard scan, and random number generation. It also digitizes the resistive paddle inputs and controls maskable interrupt (IRQ) requests from peripherals.
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