Emulating the YM2612: Part 1 – Interface

This is the first post in a series on emulating the main Sega Genesis sound chip, the Yamaha YM2612 FM synthesis chip, also known as the OPN2. To date, the YM2612 is pretty easily the most difficult-to-emulate sound chip that I have worked on. It’s not extremely complex in concept, but it has an incredible amount of specific details and quirks in how exactly it works, and many of them need to be emulated exactly correctly for game audio to sound correct. Debugging mistakes is also very, very difficult due to all of the modulation and feedback, where for example a minor mistake in envelope emulation can manifest as some instruments sounding completely wrong. These posts are not going to describe how to implement a cycle-accurate YM2612 emulator (mine is not), but I will do my best to describe how the chip works at a low level, from the perspective of someone who emulated it for the first time with modern documentation and resources available. I found a number of minor bugs and oversi ... Read full article.