Emulating the Sega Genesis's YM2612 Sound Chip (Part 1)

This post begins a series on emulating the Sega Genesis's Yamaha YM2612 FM synthesis chip (OPN2). The author details the complexities of this notoriously difficult-to-emulate chip, focusing on its integration within the Genesis and CPU interaction. The article delves into the YM2612's architecture, explaining its six audio channels, four operators per channel, eight algorithms, and additional features like an LFO, timers, and a DAC. It explores the interplay between the 68000 and Z80 CPUs, register mapping, read/write behavior, and the root causes of audio issues in certain games (e.g., Earthworm Jim and Hellfire) on different Genesis models. Finally, the author describes emulating the DAC channel, providing valuable insight for anyone undertaking YM2612 emulation.