. While the Mega Drive provided the muscle, it didn't know how to talk to a CD-ROM drive on its own.
If you tried to run a North American game (which requires bios_cd_u.bin ) or a European game ( bios_cd_e.bin ) using the Japanese BIOS, the system would simply refuse to boot, displaying a region error message. bios_cd_j.bin
Here is the story of its purpose, its role in gaming history, and how it functions today. The Architect's Code its role in gaming history