The YM3812, known more colloquially as the OPL2, is an integrated circuit created by Yamaha. Specifically, it is a programmable sound generator which creates audio waveforms using FM synthesis. The YM3812 was used in many arcade games, but was especially popular on home computer sound cards from the late 1890s to the mid-1990s, particularly in the AdLib and Sound Blaster lines.
The YM3812 outputs mono audio, but some sound cards, like the Sound Blaster Pro, linked two chips together for stereo output. It can produce 9 individual audio channels, each made of two oscillators or 6 channels with 5 percussion instruments available.
Each oscillator can produce sine waves which may also be modified into 3 other waveforms – the negative part of the sine can be muted or inverted, and pseudo sawtooth waves (1/4 sine waves upward only with silent sections in between) can also be produced. Each wave generator has its own ADSR envelope generator.
Yamaha created an entire family of chips designated OPL, which is short for FM Operator Type-L. The YM3812 is the second chip in the line and is fully backward compatible to it's predecessor, the YM3526, or OPL. In fact, the two chips are identical except for the additional 3 waveforms of the YM3812. Another near identical chip is the YM2413 or OPLL, a slimmed down version of the YM3812. The chip's successor is the YMF262 or OPL3, which was found on many 16-bit sound cards.
The YM3812 can be found on the following devices:
|1990-??-??||Creative||Sound Blaster 1.5||1|
|1990-??-??||Media Vision||Thunder Board||1|
|1991-10-??||Creative||Sound Blaster 2.0||1|
|1991-??-??||Creative||Sound Blaster Pro||2|
|1991-??-??||Covox||Sound Master Plus||1|
|1991-??-??||Media Vision||Pro AudioSpectrum||2|
|1992-05-??||Media Vision||Pro AudioSpectrum 16||?|
|199?-??-??||Creative||Sound Blaster MCV||1|
|199?-??-??||Covox||Sound Master II||1|
|199?-??-??||Media Vision||Pro AudioSpectrum 16 Basic||?|
|199?-??-??||Media Vision||Pro AudioSpectrum 16 Studio||?|
|19??-??-??||Rainbow Arts||Rainbow Arts Soundboard||1|
This list is meant to be in chronological order, but many release dates are missing.
The YM3812 has been emulated by DOSBox, MAME, and AdPlug.