The term "Reference Set" refers to a collection specifically verified to match the MAME 2003-Plus DAT file , ensuring 100% compatibility with the emulator core. The most reputable source for these sets is the Internet Archive , which hosts community-maintained preservation projects:
When searching for ROMs, you will encounter three terms: Split, Merged, and Non-Merged. Here is why is the gold standard for MAME 2003 Plus. mame 2003plus reference full nonmerged romsets link