From Sega Retro

Kega is an series of emulators by Steve Snake. Being the Windows-based successor to KGen for DOS, this went through 3 "generations".

Kega (2002)

After a long break from the emulation scene (1999-2002), Steve surprised many fans with the sudden release of an all new Windows/DirectX based emulator. It included many new features, such as Sega Master System and Mega CD emulation. To run full speed, it required at least a 500 MHz Celeron based computer. It followed the release of the very popular Gens, another Windows based Genesis emulator with excellent speed and compatibility released by Stef D in 1999.

Kega Lazarus (2003)

Kega Lazarus was so named because it was an attempt to get the emulator up to date (and beyond) after a hard disk crash caused Steve Snake to lose all his Kega sources since 0.02b (0.04b being the final release of Kega), and as a possible play on both the biblical Genesis, and Lazarus, whom Jesus resurrected from the dead. An important feature during the development of Lazarus was the addition of 32x support, although at first compatibility wasn't great.

Kega Fusion (2005)

The final (and current) version of Kega is named "Fusion", because it is in spirit a fusion of Kega and Kega Lazarus with even more features and compatibility. It was the first version to support hardware accelerated blitters via Direct3D, as well as vastly improved 32x support.