ClownMDEmu - RetroBIOS

Type	standalone + libretro
Source	https://github.com/Clownacy/clownmdemu-libretro
Version	Git
Profiled	2026-03-18
Cores	clownmdemu
Systems	sega-megadrive, sega-megacd

No BIOS or firmware files required. This core is self-contained.

ClownMDEmu is a Sega Mega Drive/Genesis and Mega CD emulator by Clownacy. Supports cartridge (bin/md/gen) and CD (cue/iso/chd) formats, plus a subsystem for cartridge+CD combo (Mega CD Mode 1).

The core has NO external BIOS file requirements. firmware_count = 0 in the libretro .info file confirms this.

Mega CD boot ROM: a custom open-source replacement boot ROM is compiled directly into the binary as a 16384-entry uint16 array (mega-cd-boot-rom.c included into bus-main-m68k.c:19-21). Source at https://github.com/Clownacy/clownmdemu-mcd-boot. No external CD BIOS files (bios_CD_E.bin, bios_CD_U.bin, bios_CD_J.bin) are needed or loaded.

TMSS (Trademark Security System): not implemented at all. No TMSS ROM is loaded or checked. The core boots games directly without the "Produced by or under license from Sega" screen.

The system directory (RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY) is only used as a fallback path for Backup RAM (BuRAM) save files, not for BIOS loading.

CD add-on can be enabled for cartridge games via the "clownmdemu_cd_addon" core option to allow CD music features, but this uses the built-in boot ROM, not an external BIOS.

The core implements its own Mega CD BIOS call handler (MegaCDBIOSCall in bus-sub-m68k.c) via HLE (high-level emulation) of Sub-CPU BIOS functions including CDBIOS, CDCTRN, FDRSET, FDRCHG, DRVINIT, CDCSTOP, CDCSTAT, CDCREAD, and others.

Generated on 2026-03-20T19:12:20Z