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). 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).
However, Fusion is highly optimized and runs very efficiently. 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).