The Sega Saturn region free BIOS replaces the region locked chip inside the console and allows import games to play.
Unlike the switchless multi-region mod, the region free BIOS does not affact the video rate of games. It will not force a PAL console to play in 60Hz or an NTSC console to play in 50Hz. It only affects the ability of games to load. For this reason usually a second mod is required to switch between 50 and 60 hertz.
The only benefit of a region free BIOS over a switchless multi-region mod is that the region of the console does not have to be manually set before a game can load.
There are a number of different BIOS types for different consoles and countries, but they are all compatible with each other.
Only surface mount BIOS chips are currently available which are not compatible with the VA0 Sega Saturn mainboard revision. VA0 requires a DIP chip. DIP BIOS chips will be available soon.