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YM2608B - On Board.jpg
Developer: Yamaha
Released: c. 1985
Type: Chip

1.) Square Wave/Noise
2.) Square Wave/Noise
3.) Square Wave/Noise
4.) FM Synthesis
5.) FM Synthesis
6.) FM Synthesis
7.) FM Synthesis
8.) FM Synthesis
9.) FM Synthesis
10.) ADPCM (variable rate)
11.) ADPCM rhythm
12.) ADPCM rhythm
13.) ADPCM rhythm
14.) ADPCM rhythm
15.) ADPCM rhythm
16.) ADPCM rhythm

The YM2608 or LSI Operator Type-N Model A, known simply as the OPNA, is an integrated circuit created by Yamaha used to create audio wave forms using four distinct methods. The chip came onto the market sometime around 1987. YM2608 is probably best known for its inclusion in the PC-8801 and PC-9801 lines of Japanese personal computers.

The YM2608 consists of four internal modules:

  • SSG Sound Source - A complete internal implementation of the Yamaha YM2149 which can produce three channels of pulse wave synthesis and one noise channel.
  • FM Sound Source - A six-channel FM synthesis sound system, based on the YM2203 (the original OPN).
  • ADPCM Sound Source - A single channel for samples in 8-bit ADPCM format at a sampling rate between 2-16kHz.
  • Rhythm Sound Source - A six-channel ADPCM system, enabling playback of six percussion "rhythm tones" from a built-in ROM

The YM2608 was revised at least twice identified as the YM2608A and YM2608B.


The following devices implemented the YM2608:

Release Company Device Notes
1987-??-?? NEC PC-8801-23 An internal sound card for the PC-8801.
1987-??-?? NEC PC-9801-86 An internal sound card for the PC-9801.
1992-01-?? NEC PC-9801 NEC began building these directly into the motherboards around this time.
199?-??-?? NEC PC-8801 NEC began building these directly into the motherboards around this time.


YM2608 output was featured in hundreds of games from 1987 to the late 1990s between the PC-8801 and PC-9801 computer lines from NEC.

Picture Gallery


Document Download
Manual (Translated from Japanese) Download - (info)

Emulation Status

The YM2608 emulation exists in most comprehensive PC-8801 and PC-9801 emulators.