1.) Square Wave
The SN76489 is a family of PSGs designed by Texas Instruments and released in the early 1980s. Each version of the chip features 3 square wave channels and 1 noise channel. Each channel's volume can be set from 0 to 15. The noise channel can be put into either periodic noise or white noise mode. This was a significant improvement on their earlier chip, the SN76477 and gave rise to copycats emulating TI's 3 Voice Chipset. These improvements made the SN76489 series widely popular throughout the 1980s, even seeing use in home videogame systems all the way up until the turn of the century, but it couldn't overtake the AY-3-8910 which dominated the audio chip market at the time.
Minor additions were made to each model in the family, but each is backward compatible to the previous models.
Original is SN76489, narrow version is SN76489N, revised is SN76489A, revised narrow is SN76489AN.
Original is SN76494, narrow version is SN76494N, revised is SN76494A, revised narrow is SN76494AN. Unlike the SN76889, which doesn't use pin 9, the SN76494 utilizes the pin for audio input.
Original is SN76496, narrow version is SN76496N, revised is SN76496A, revised narrow is SN76496AN. Like the SN76494, pin 9 is used for audio input.
The chip was cloned by NCR who produced the very similar NCR 8496. However, the clone never took off and appears to have only been used in the Tandy 1000 line of computers. The chip was also used in Sega's Game Gear, adding a stereo effect.
Over the years, a number of computers, video game consoles, and peripheral devices used the SN76496. This is a chronological breakdown of those devices.
|1984-03-??||PCjr 3 Voice||SN76496N x1|
|1984-11-??||Tandy 3 Voice||?|
|1998-10-28||Neo Geo Pocket||?|
|1999-03-16||Neo Geo Pocket Color||?|
|Unreleased (c. 1983)||TI 99/8||SN76494N x1|
The SN76489 series didn't see the popularity of it's competitor the AY-3-8910, but it did see a lot of use in the early 1980s.
According to the MAME arcade database, the first time a SN76489 chip appeared on an arcade game was 1980 on Space Force. However, this may be a mistake since it sites the use of three SN76496 chips, but it is unlikely that these particular chips were manufactured until around 1983.
There was an increase in the usage of the SN76489 in 1982 to close to 10 different cabinets, and the chip overtook the older SN76477 model. However, Texas Instruments wasn't even making a dent in the AY-3-8910 market which had about 10 times the popularity.
|SN76489AN Manual||Download - (info)|
|SN76494 / SN76496 Manual||Download - (info)|
Due to the chip's popularity, it has been emulated several times.
- DOSBox emulates it for PCjr and Tandy support.
- MAME has emulated it for the various arcade games that require it.
- Any console or computer emulator in the list of devices above that has music must emulate some version of the SN76489.