Kega Fusion

From Sega Retro

Video game console emulator

Kega Fusion
System(s): Sega Mega Drive, Mega-CD, 32X, Master System, Game Gear, SG-1000, SC-3000
OS: Windows, Linux, Mac OS X
Developer: Steve Snake
Programmed in: Assembly, C
Last release date: (14 years ago)
Last version: 3.64

Kega Fusion, also shortened as Fusion and initially named Kega II, is a multi-system emulator for Windows, Linux and Mac OS X developed by Steve Snake. It is the follow-up to Kega Lazarus, and is the last in Steve Snake's Sega emulators after KGen, KGen98, Kega and Lazarus.

The first few versions of Fusion were numbered 0.1 followed by a letter. This system was dropped due to people's reluctance to use lower-numbered versions of any program, and Steve Snake decided to jump straight to version 3.0. After version 3.2 the emulator was no longer referred to as a "beta" for the same reason.


Unlike most Mega Drive emulators of the time, Kega Fusion puts an extremely high importance on accuracy as opposed to speed or other features (such as netplay, movie recording, or many other features found in emulators like Gens). However, Fusion is highly optimized and runs very efficiently. On a Pentium III class or a similar microprocessor, Kega Fusion runs at 60 frames per second with Sega Mega Drive ROMs, though with the popular 2xSaI graphics filter plugin the processing power needed to achieve 60 frames per second is much higher (it can also be noted that emulating Sega 32X ROMs at full speed, an 850 MHz or faster microprocessor is strongly recommended). The emphasis on accuracy shows in the Yamaha YM2612 coding, which is reported by Steve Snake to be almost perfect (indeed, there are many games where sound is buggy or wrong in any Mega Drive emulator except for Kega Fusion such as the title screen themes for Sonic 3D: Flickies' Island and Sonic & Knuckles). Compatibility is very high with Kega Fusion, even on the infamous Sega 32X, which has many games that most if not all emulators cannot handle. Since the Sega 32X BIOSs have been more thoroughly reverse engineered than the BIOSs for the Mega-CD, as of version 3.3 Kega Fusion does not require a Sega 32X BIOS (though you can still use an external BIOS). Kega Fusion can emulate most (if not all) Sega home video game consoles released before the Sega Saturn (though there is some cryptic indication by Steve Snake that Saturn emulation could be possible in the future).

Along with being able to emulate most Sega home console systems Kega Fusion also supports logging to a WAV file or the successor to GYM format, VGM. VGM is much like GYM in terms of how it's created but widely superior in its accuracy to YM2612 synthesis, compression (in the VGZ format) and looping. It also has support for the YM2413, a synthesizer found on the Sega Mark III (the Japanese equivalent of the Master System), which the GYM format does not. As of version 3.5, Kega Fusion supports multiplayer over the internet or LAN. While multiplayer support is still in its preliminary stages, Kega Fusion 3.51 has made multiplayer more stable. Kega Fusion 3.6 currently supports AVI movie logging in the form of a "Video 1 lossless codec."

Even though Kega Fusion is being developed separately from Gens, the development teams are more cooperative than antagonistic towards each other. The differences between Kega Fusion and Gens appeal to different audiences, with Kega Fusion having a more hardcore audience mainly because Kega Fusion is not as well known among new and/or novice emulation fans as Gens even though it is much more accurate.

It is highly recommended to enable "Perfect Sync" option when playing Mega-CD games, as Kega Fusion will not be able to run some of them properly with this setting disabled.

The Game Gear game Ax Battler: A Legend of Golden Axe has no sprites in version 3.64, making it unplayable. Another Game Gear game Kaitou Saint Tail has graphical artifacts as well, such as when powerup us used. Use version 3.63 of Kega Fusion for these games.



Download Kega Fusion
Multiple downloads available

Old versions

  • Kega Fusion versions 0.1 to 3.63 (info) (3.62 MB)
    • Kega Fusion v0.1 (2004-07-16)
    • Kega Fusion v0.1b (2004-07-18)
    • Kega Fusion v0.1c (2004-07-20)
    • Kega Fusion v0.1d (2004-07-22)
    • Kega Fusion v0.1e (2004-11-14)
    • Kega Fusion v3.0 (Maple) (2005-02-17)
    • Kega Fusion v3.1 (2005-02-xx) (missing; glitchy)
    • Kega Fusion v3.11 (2005-02-22)
    • Kega Fusion v3.2 (2005-02-28)
    • Kega Fusion v3.3 (2005-06-25)
    • Kega Fusion v3.4 (2005-07-14)
    • Kega Fusion v3.5 (2006-01-02)
    • Kega Fusion v3.51 (2006-01-06)
    • Kega Fusion v3.51 edited for Chaotix prototypes (2008-02-24)[2]
    • Kega Fusion v3.6 (2008-12-10)
    • Kega Fusion v3.61 (2008-12-24)
    • Kega Fusion v3.52i (Mac OS X) (2008-12-25)
    • Kega Fusion v3.62 (Windows/Linux/Mac OS X) (2009-09-28)
    • Kega Fusion v3.63 (Windows) (2009-10-07)

External links