From Sega Retro
Genecyst was a popular Sega Mega Drive emulator for DOS by Bloodlust Software (the same team that made NESticle). Until the release of Gens, it was widely regarded to be the best Genesis/Mega Drive emulator with the nearest competitor being KGen. Genecyst introduced the still very popular savestate format .gsx and music logging format .gym.
Since Gens appeared with many features such as Sega Mega-CD emulation, as well as having a Microsoft Windows-based GUI, Genecyst has been left on the shelf. It is still remarkably fast on older CPUs, and has a number of useful features such as real-time VRAM and palette viewing. It can also be used to convert SMD format Mega Drive ROMs to BIN format.
The emulator is no longer updated.