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POKEY

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A sound-generating integrated circuit, designed by Atari and used in their early-1980s video games, and also the model 400 and 800 microcomputers. The IC contained a basic analog synthesis capability, under control of the computer's software. It was polyphonic, capable of generating up to four voices, although pitch accuracy suffered when more than one voice was used at a time, due to the chip's control architecture.

Each voice consisted of a VCO, capable of generating an imperfect pulse wave and offering pulse width modulation; a high pass VCF, and a VCA. There was also random-number generator and shift register that could be used to distort the signal, or as a noise source. (There was no lowpass filter capability; the designers may have felt it was unnecessary given the extremely limited bandwidth of sound reproduction in the gaming systems of the day.) All controllable parameters were controlled by software, by writing parameter values to registers on the chip. There was no modulation capability; any desired modulation or envelope generation had to be performed in software. The IC also included a number of capabilites unrelated to the sound generation function but useful in games, such as panel scanning and video timers.

The POKEY gave Atari games of the era a unique sound. The imperfect waveform from the VCO, and the lack of low pass filtering, forced certain compromises, such as often using square waves, or duty cycles near to square, in order to achieve a full sound. Clever use of the distortion could result in surprisingly thick bass sounds, and programmers learned to take advantage of the pitch inaccuracies to produce chorusing effects.

The type of video-game-associated music produced with POKEY and similar ICs from that era is now referred to as chiptunes, and the POKEY sound is much sought out for the purpose. Since the actual POKEY is long out of production and nearly unavailable, several emulators have been developed.

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