Genecyst was a popular Sega Mega Drive/Genesis emulator for DOS

DOS

DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

, by Bloodlust Software

Bloodlust Software

Bloodlust Software is a developer of humorous PC computer games. It was originally formed in 1992 by two high school students who were angry at the rise of movements against computer game violence...

 (the same team that made NESticle

NESticle

NESticle was a popular NES emulator for DOS, created by Sardu of Bloodlust Software. The name is a portmanteau of "NES" and "testicle"....

). Due to its high speed and then-good YM2612 emulation (in version x.xx), it was widely regarded as the all-around best Mega Drive/Genesis emulator on the scene, with the nearest competitor being KGen. Genecyst has since been supplanted by newer emulators Gens

Gens (Emulator)

Gens is a free Sega Genesis emulator. It runs on Windows systems , on Linux and on Microsoft's Xbox. A port to the Sega Dreamcast, known as Gens4All, is currently in development. Development of Gens began in 1999...

 and Kega Fusion.

The program requires an Intel Pentium (or later x86-based) CPU for full speed emulation. The emulator is however compatible with DOSBox

DOSBox

DOSBox is emulator software that emulates an IBM PC compatible computer running MS-DOS. It is intended especially for use with old PC games. DOSBox is free software....

as well.