Yamaha YM2610

YM2610, aka OPNB, is a fifteen-channel sound chip developed by Yamaha. It's a member of Yamaha's OPN family of FM synthesis chips, and related to the YM2608. It was most notably used in SNK's Neo Geo arcade and home game systems, along with other arcade game system boards, such as the Taito Ninja Warriors and Taito B System. The YM2610 was used in conjunction with a YM3016 stereo DAC.

The YM2610 has the following features:
 * Four concurrent FM synthesis channels (voices), four operators per channel
 * Three SSG channels
 * One programmable noise channel
 * ADPCM-A: 6 ADPCM channels, 18.5 kHz sampling rate, 12-bit audio depth
 * ADPCM-B: 1 ADPCM channel, 1.85–55.5 kHz sampling rate, 16-bit audio depth
 * Two interval timers
 * A low frequency oscillator (LFO)

The YM2610B variant added two extra FM synthesis channels for a total of six, but was identical in every other feature. It was used in Taito's arcade boards, such as the Taito Z System, amongst others.