bios-cd-u.bin bios-cd-e.bin bios-cd-j.bin essential system firmware (BIOS) files required to run (or Mega-CD) games on various emulators and mini consoles
Are you setting this up on a specific device like a , Miyoo Mini , or PC ? Knowing your hardware can help provide exact folder paths for your installation. Sega CD games not loading - RetroPie Forum
To play Sega CD games on modern platforms—such as using the Genesis Plus GX or PicoDrive cores—these files must be placed in a specific "system" folder.
Known as the "Mega-CD" BIOS. This is required for European releases. Note that because PAL games run at 50Hz, using this BIOS on a non-optimized screen can sometimes lead to the "letterboxing" effect or slightly slower gameplay compared to the NTSC versions. bios-cd-j.bin (Japan):