The BIOS is essentially the firmware. It handles the initial hardware checks and the region encoding. If your BIOS region doesn't match your ROM region, you will likely see a "Region Error" or a black screen upon startup. Where to Find the Naomi Boot .bin
Instead, they require the user to supply these files separately. When an emulator loads a Naomi game, it needs the BIOS to: naomi boot .bin bios download