2610b

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. It was most notably used in SNK's Neo Geo arcade and home game systems, along with other arcade game systems. The YM2610 was used in conjunction with a YM3016 stereo DAC.
The YM2610 has the following features:

Four concurrent FM channels (voices), four operators per channel, DAC compatible with YM3016
Three SSG channels: compatible with YM2149 (Atari ST)
One programmable noise channel
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, 18.5–55.5 kHz sampling rate
Two interval timers
A low frequency oscillator (LFO)The YM2610B variant added two extra FM channels for a total of six, but was identical in every other feature. It was used in Taito's arcade boards, including the Taito Z System.

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