Yamaha YM2610

The YM2610, a.k.a. OPNB, is a sound chip developed by Yamaha. It is a member of Yamaha's OPN family of FM synthesis chips, and related to the YM2608.
The YM2610 was most notably used in SNK's Neo [Geo (console)|Neo Geo] arcade and home video game systems from 1990 along with other arcade game systems, which included Taito's arcade [system boards] from 1987 such as the Taito Z System, which used a variant of the YM2610.
The YM2610 has the following features:

Four concurrent FM synthesis channels
Four operators per channel
Two interval timers
A low frequency oscillator
Three SSG square wave tone/noise channels: compatible with YM2149
Seven adaptive differential pulse-code modulation channels:
*ADPCM-A: Six ADPCM channels, fixed pitch, 18.5 kHz sampling rate at 12-bit from 4-bit data
*ADPCM-B: One ADPCM channel, variable pitch, 2–55.5 kHz sampling rate at 16-bit from 4-bit data

A variant of the YM2610 known as the YM2610B was identical to the YM2610 in every other feature, except that it added two extra FM channels for a total of six. The YM2610 and YM2610B is used in conjunction with a YM3016 stereo DAC.