In the 0.078 reference set, ROMs are distributed as .zip archives. Each zip file contains the dumped memory chips (EPROMs) from an arcade PCB.
In the world of arcade emulation, newer isn't always better. While modern versions of MAME prioritize 100% accuracy, that precision requires massive processing power. MAME 2003 Reference Set - MAME 0.078 ROMs- CHDs...