: FBNeo is a "rolling release" emulator, meaning it is constantly updated. If you use a romset from three years ago with a core updated last week, the internal requirements for that game may have changed.
For Neo Geo games:
Do mix MAME and FBNeo ROMs. Get a full FBNeo ROM set (e.g., from archive.org or a ROM manager like ClrMamePro ). fbneo romset unknown
If your FBNeo expects a but you only downloaded a single clone file, you get the "unknown romset" error. : FBNeo is a "rolling release" emulator, meaning
Why does a perfectly good-looking ROM file get rejected? Usually, it boils down to one of four scenarios. fbneo romset unknown