Master System

RetroBat system	mastersystem
Games go in	roms\mastersystem
BIOS	Only for BizHawk's SMSHawk, fetched when your library has it
Tested rows	Platforms lists each emulator and whether it passed

Which emulator to use

Leave RetroBat on its default, RetroArch with the Genesis Plus GX core. Avoid RetroArch's FBNeo core: it does not start games named the way RomM libraries usually name them, because FBNeo expects its own file names.

Kega Fusion keeps its in-game saves inside its own program folder rather than in saves. RomMBat syncs them from there, along with its save states. Its controls need setting up in Kega's own menu before your pad works.

BIOS

Only BizHawk's SMSHawk needs a BIOS, and it refuses to start any game without one. Every other emulator starts without.

Upload these to RomM, under any name, and a sync fetches them under the names SMSHawk looks for:

For	The BIOS	md5
A USA or European game	Master System (USA, Europe) v1.3	840481177270d5642a14ca71ee72844c
A Japanese game	Master System (Japan) v2.1	24a519c53f67b00640d0048ef7089105
A Korean game	Master System (Korea)	e49e63328c78fe3d24ae32bf903583e0

The first two also land as the copies some RetroArch cores read under their own names, such as bios_U.sms, though those cores start without them. The firmware matrix lists every file and which emulator reads it, and BIOS and firmware covers what to do when your library lacks one.

Saves

A save follows you to another emulator only where the two read the same file (Changing emulator). On the Master System, RetroArch's Genesis Plus GX and PicoDrive cores share one save. The rest each keep their own.

Known issues

The standalone Mednafen will not start a game after the standalone Mesen has saved it. Mednafen opens Mesen's save file, cannot read it, and stops. Move that save out of saves\mastersystem to play the game under Mednafen. A sync does not bring another computer's Mesen save down for a game that runs under Mednafen here, though restoring one by hand does.