emulator: ClownMDEmu
type: libretro
source: "https://github.com/libretro/clownmdemu-libretro"
profiled_date: "2026-03-18"
core_version: "Git"
display_name: "Sega - MD/CD (ClownMDEmu)"
cores:
  - clownmdemu
systems:
  - sega-megadrive
  - sega-megacd

notes: |
  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.

files: []

analysis:
  tmss:
    supported: false
    notes: |
      TMSS is not implemented. No ROM loaded, no "Produced by Sega" check.
      No references to TMSS exist anywhere in the codebase.

  megacd_bios:
    external_required: false
    builtin_boot_rom: true
    boot_rom_source: "https://github.com/Clownacy/clownmdemu-mcd-boot"
    boot_rom_location: "source/mega-cd-boot-rom.c (16384 uint16 entries = 32 KB)"
    bus_mapping: "0x400000-0x41FFFF (address & 0x20000 == 0)"
    source_ref: "bus-main-m68k.c:19-21, bus-main-m68k.c:484-494"
    bios_hle: true
    hle_source_ref: "bus-sub-m68k.c:64 (MegaCDBIOSCall)"
    notes: |
      The Mega CD boot ROM is an open-source replacement compiled into the
      binary. Sub-CPU BIOS calls are handled via HLE. No external Sega CD
      BIOS files (bios_CD_E/U/J.bin) are needed.