Editing Atari 8-bit computers (section)

=== POKEY ===

[[POKEY]] is a custom chip used for reading the keyboard, generating sound and serial communications (in conjunction with the [[Peripheral Interface Adapter]] chip) commands and IRQs, plus controlling the 4 joystick movements on the 400 and 800 models, and later RAM banks or ROM (OS/BASIC/Self-test) enables for XL/XE lines.<ref>Mapping The Atari, Ian Chadwick and Atari 130XE owner's manual</ref> It provides timers, a [[Random number generation|random number generator]] for generating acoustic [[noise]] and random numbers, and [[maskable interrupt]]s. POKEY has four semi-independent audio channels, each with its own frequency, noise and volume control. Each 8-bit channel has its own audio control register which select the noise content and volume. For higher sound frequency resolution (quality), two of the audio channels can be combined for more accurate sound (frequency can be defined with 16-bit value instead of usual 8-bit). The name POKEY comes from the words "POtentiometer" and "KEYboard", which are two of the I/O devices that POKEY interfaces with (the potentiometer is the mechanism used by the [[Paddle (game controller)|paddle]]). The POKEY chip—and its dual- and quad-core versions—was used in many Atari coin-op arcade machines of the 1980s, including ''[[Centipede (video game)|Centipede]]'' and ''[[Millipede (video game)|Millipede]]'',<ref>[http://www.brasington.org/arcade/cm/trouble.shtml Multipede—Trouble shooting guide], Braze Technologies</ref> ''[[Missile Command]]'', ''[[Asteroids Deluxe]]'', ''[[Major Havoc]]'', and ''[[Star Wars: Return of the Jedi (video game)|Return of the Jedi]]''.