Yamaha YM2608

YM2608, a.k.a. OPNA, is a sixteen-channel sound chip developed by Yamaha. It's a member of Yamaha's OPN family of FM synthesis chips, and the successor to the YM2203. It was notably used in NEC's PC-8801/PC-9801 series computers.

The YM2608 comprises four internal modules:

The FM Sound Source module includes six concurrent FM channels (voices, twice as many as the Yamaha YM2203), four operators per channel, with dual interrupt timers and an LFO. It also includes eight possible operator interconnections, or algorithms, for producing different types of instrument sounds.

The SSG, or Software-controlled Sound Generator, is Yamaha's YM2149 programmable sound generator. The YM2608 includes the SSG's 3 sound channels and dual 8-bit GPIO ports.

The YM2608 is used with a YM3016 stereo DAC.

The YMF288, a.k.a. OPN3, is a development of the YM2608, used in later NEC PC-9801 computer soundcards. It removes the YM2608's GPIO ports, CSM-mode and the ADPCM Sound Source. It also reduces the wait times on register access, and adds a low-power standby mode. The YMF288 also came in a much smaller physical 28-pin SOP and 64-pin QFP packages.

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