it is a 4 channel PCM sound source used by Irem in their arcades in late 1980s and early 1990s, often paired with Yamaha YM2151.
the sound chip itself is rather unremarkable, having 8-bit volume and pitch control and no stereo panning...
none
let's be honest. Furnace has too many chips and a great portion of them are sample chips that do the same task: playing back samples.
this chip uses the GA20 instrument type.