You have your bios-cd-u.bin in the right folder, but Sonic CD is still stuck on a black screen. Here is the checklist:
The green text changed one last time.
These three files are the required to run Sega CD (Mega-CD) games on most modern emulators, such as RetroArch (using the Genesis Plus GX or PicoDrive cores). They act as the operating system for the emulated hardware and are strictly categorized by region. BIOS Region Breakdown sega cd bios-cd-e.bin bios-cd-j.bin bios-cd-u.bin
You have your bios-cd-u.bin in the right folder, but Sonic CD is still stuck on a black screen. Here is the checklist:
The green text changed one last time.
These three files are the required to run Sega CD (Mega-CD) games on most modern emulators, such as RetroArch (using the Genesis Plus GX or PicoDrive cores). They act as the operating system for the emulated hardware and are strictly categorized by region. BIOS Region Breakdown