The Universe BIOS (or UniBIOS) is a patched MVS System ROM maintened by Razoola, which can run on both MVS and AES. It wasn't written from the ground up but built over the original (copyrighted) SNK system ROM code and data.
An alternative to the Universe Bios there is the Neopen BIOS.
Difference with SP-S2:
- Cheat database with in-game menu
- Jukebox function
- Error handling