What a ROM set is A "ROM set" for MAME is a collection of ROM images — binary dumps of the read-only memory chips from arcade PCBs (printed circuit boards) — organized so that MAME can load and emulate the original hardware and run the games as they behaved on the arcade machines. A MAME 0.250 ROM set specifically contains the ROM images, BIOS files, and ancillary data matched to the codebase and datfile expectations of MAME version 0.250. Those ROMs are typically named, merged, or split to match the emulator's driver definitions and to ensure checksums and file sizes line up with MAME's internal mapping.