Dreamcast — Bios Flycast [new]

Place BIOS files in RetroArch’s (default: retroarch/system/ ).

So, take the time to set up your BIOS correctly. Listen for that jingle. Watch that swirl. And then enjoy the last great console of the 20th century on your 4K monitor—running flawlessly, thanks to the tiny, 2-megabyte heart of the Dreamcast. Dreamcast Bios Flycast

Simpler approach for most users: Use a pre-dumped, verified BIOS from your own console’s disc drive + a boot CD like to run dumping tools. thanks to the tiny

The reason is architectural. Cartridge-based consoles (like the SNES or Genesis) execute code directly from the cartridge. The BIOS wasn't strictly necessary for most games after booting. Dreamcast Bios Flycast

Flycast allows you to swap BIOS files to change the "region" of your virtual console.