@acris I'm sorry but i deleted the rebuild, to do it again. I've been researching and found out that it's something about Clrmame's options, "Merge/Non-Merge roms" that creates derived roms based on information from the .dat file used. In the instructions i found, it is necessary to choose "Non-Merge roms" in Clrmame for the rebuild to work on FBNeo. I could choose "Merge-roms" but i don't know if the roms will work, or how many will work, in Retroarch. Any tips? Edit: I'm doing tests at Clrmame but i'm confused. I downloaded a recent romset for FBNeo and it says that RetroArch users should rebuid the romset. I'm doing everything according to the instructions of the author of the romset, using a tutorial from Clrmame and using a Libretro .dat file for FBNeo-NeoGeo games. Besides the result being roms with many variants as i said before, apparently some roms are not working. In contrast, i tried to use the romset roms without rebuilding and these roms work. Anyway... I don't know if i should rebuild the romset or use the roms as they are. They create new emulators, new romsets but lay users are unable to run the games because of the above problems and the information is scarce and sparse. I was using an old version of Recalbox and came to a new version and suddenly my roms don't work and the information on how to fix this is hard to find. But I know that the creators of Recalbox are not to blame for that. My problem here is not even with Recalbox.