Please use a bios that matches your models Sega CD as Model 1 bioses will not work in Model 2 consoles and vice-versa due to the bios being programmed for the disc loading style between these consoles.
There are currently some Japanese Mega CD game compatibility issues with all USA and European bioses. For 100% compatibility, it is recommended to use a Japanese bios or do a dual bios mod. Japanese Mega CD bioses are compatible with USA consoles, but Japanese Mega CD bioses will not work in European consoles with the exception of one bios. For a list of games that have compatibility issues, please see below
Games that work with USA (NTSC-U) and European (PAL) bioses that have a very minor graphical issue:
Gambler Jikocyushinha 2 (First copyright screen has slight corruption, but over all works 100%)
Games that work with USA (NTSC-U) and European (PAL) bioses while pressing C and Start after disc loading is completed:
Aisle Lord
Fhey Area
Games that are currently not working with USA (NTSC-U) and European (PAL) bioses:
Heavy Nova
Ishii Hisaichi no Daisekai
Sengoku Densyo
There are currently some Japanese Mega CD game compatibility issues with all USA and European bioses. For 100% compatibility, it is recommended to use a Japanese bios or do a dual bios mod. Japanese Mega CD bioses are compatible with USA consoles, but Japanese Mega CD bioses will not work in European consoles with the exception of one bios. For a list of games that have compatibility issues, please see below
Games that work with USA (NTSC-U) and European (PAL) bioses that have a very minor graphical issue:
Gambler Jikocyushinha 2 (First copyright screen has slight corruption, but over all works 100%)
Games that work with USA (NTSC-U) and European (PAL) bioses while pressing C and Start after disc loading is completed:
Aisle Lord
Fhey Area
Games that are currently not working with USA (NTSC-U) and European (PAL) bioses:
Heavy Nova
Ishii Hisaichi no Daisekai
Sengoku Densyo