Texas Instruments · 1979 · 1980s · 3 voices
The SN76489 was a simple three-voice PSG with noise that appeared in dozens of consumer products, most notably the Sega Master System and as the secondary sound chip on the Mega Drive, providing its characteristic square-wave chirps and hissing percussion.
Texas Instruments introduced the SN76489 in 1979 as a low-cost Programmable Sound Generator offering three tone generators and one noise generator in a single inexpensive package. Each tone channel produced a square wave at a programmable 10-bit frequency with 4-bit attenuation; the noise channel could generate either white noise or periodic noise (a buzzing tone). The chip appeared in numerous consumer products including the ColecoVision, BBC Micro, and Sega's SG-1000 before becoming the primary audio chip of the Master System. On the Sega Mega Drive, the SN76489 was retained alongside the more powerful YM2612 FM chip as a secondary PSG, providing backward-compatibility tones and supplementary sound effects. Its simplicity made it a popular choice for cheap consumer electronics through the 1980s, and its pinout was compatible with enough systems that several clones and compatible chips were produced.