: The primary system BIOS. Sometimes found online as dc_bios.bin , it must be renamed to dc_boot.bin .
The BIOS is region-locked. If you use a Japan BIOS, Japanese games will boot directly; others will require a region-changer or a boot disc.
If the VMU screen is garbled or saves are not working, the dc_flash.bin file may be corrupted or missing. Deleting the file and allowing Flycast to generate a new flash image often resolves this, though it will reset the system clock settings.
The Dreamcast BIOS for Flycast! That's a great project.