bios-cd-e.bin , bios-cd-u.bin , and bios-cd-j.bin represent a shorthand for region-specific BIOS dumps of CD-based consoles, most likely the Sega CD / Mega-CD. They are not official filenames but have become a de facto standard in certain emulation circles. To use them correctly, place them in your emulator’s BIOS folder, rename as required by your specific emulator, and ensure they are legal dumps of hardware you own.
The Sega CD Troubleshooting Guide: Mastering bios-cd-e, u, and j bios-cd-e.bin bios-cd-u.bin bios-cd-j.bin
PS1 BIOS files are usually named scph1001.bin , scph5500.bin , scph5502.bin , etc. However, some simplified emulator launchers might use bios-cd-u.bin to indicate the US PS1 BIOS. This is extremely rare. bios-cd-e
The Neo Geo CD also requires a BIOS. While typical names are neocd.bin or neocd_z.rom , some frontends or custom builds have used bios-cd-j.bin for the Japanese Neo Geo CD BIOS (since Neo Geo CD was primarily popular in Japan). The Sega CD Troubleshooting Guide: Mastering bios-cd-e, u,
(known as the Mega-CD outside North America) on platforms like