emulator: beetle_saturn
type: libretro
core_classification: community_fork
core: mednafen_saturn_libretro
source: "https://github.com/libretro/beetle-saturn-libretro"
upstream: "https://mednafen.github.io/"
profiled_date: "2026-10-05"
source_commit: "65f05fa66f83e65e33be83aa433d883b4fd9509a"
core_version: "v1.32.1"
display_name: "Sega - Saturn (Beetle Saturn)"
cores:
  - mednafen_saturn
  - beetle-saturn
systems:
  - sega-saturn
  - sega-stv

notes: |
  Libretro port of Mednafen's Saturn emulation module, converted to C and
  reporting v1.32.1 (libretro.c:57). Every firmware file is read from the
  system directory: MDFN_MakeFName joins retro_base_directory and the bare
  name for MDFNMKF_FIRMWARE (libretro.c:2267-2268), and the BIOS path is
  built the same way (mednafen/ss/ss.c:1867-1869).

  Region comes from the disc header and the region table of
  mednafen/ss/db.c (libretro.c:1147-1149) and can be forced by the
  beetle_saturn_region option (libretro.c:488-510, libretro.c:1153-1154).
  With no content loaded the region defaults to North America
  (libretro.c:1103, libretro.c:1300-1301). The BIOS filename is hard-coded
  per region (mednafen/ss/ss.c:1845-1848): sega_101.bin for Japan and Asia
  NTSC, mpr-17933.bin for every other area. The file must be exactly 524288
  bytes and InitCommon returns false when it is absent, of another size or
  short on read (mednafen/ss/ss.c:1943-1947, mednafen/ss/ss.c:1961-1984).
  The sha256 of the loaded image is kept only to refuse a save state made
  under another BIOS (mednafen/ss/ss.c:1988, mednafen/ss/ss.c:2589-2608).
  ss.bios_sanity answers true (mednafen/settings.c:50-51) but nothing in the
  port reads it: the name and hash table that upstream checks under that
  setting is not carried over.

  The cartridge is chosen by the game table of mednafen/ss/db.c or by the
  beetle_saturn_cart option (libretro.c:512-530, libretro.c:1157-1158). The
  KOF95 and Ultraman ROM carts are opened from the system directory under
  the names of mednafen/settings.c:62-65 (mednafen/ss/cart.c:197-216). An
  absent file leaves the cart slot on the dummy handlers and the load goes
  on (mednafen/ss/cart.c:209).

  ST-V content is a game ZIP or a bare ROM matched against the ST-V game
  table (libretro.c:1207-1227, libretro.c:1261-1281). The cabinet region of
  the matched game selects one of three ST-V BIOS images
  (mednafen/ss/ss.c:1829-1843), and the beetle_saturn_region option is not
  applied on that path (libretro.c:1217, libretro.c:1275). The image is read
  as a bare file from the system directory or, when that file is absent, as
  the member of the same name in stvbios.zip there, matched without regard
  to case (mednafen/ss/ss.c:1875-1949, zip_reader.c:358-365). Either form
  may be 131072 or 524288 bytes (mednafen/ss/ss.c:1911-1912,
  mednafen/ss/ss.c:1962).

  The Video CD Card is driven through the CD block. With the
  beetle_saturn_mpeg_card option enabled (libretro.c:578-586, default
  disabled), CDB_Init opens mpeg_card.bin in the system directory and
  MPEG_Init keeps up to 0x80000 bytes of it (mednafen/settings.c:52-53,
  mednafen/settings.c:68-69, mednafen/ss/cdb.c:1315-1332,
  mednafen/ss/mpeg.c:423-450). The bytes are never mapped or executed: the
  loaded image only makes the card authenticate (mednafen/ss/mpeg.c:667-675).

  No setting names a file for the bootable ROM cart: ss.cart.bootrom_path
  has no value in the port (mednafen/ss/cart.c:242-262,
  mednafen/settings.c:60-71).

files:
  - name: "sega_101.bin"
    system: sega-saturn
    region: [japan, asia-ntsc]
    required: true
    size: 524288
    validation: {core: [size], upstream: [size, sha256]}
    sha256: "dcfef4b99605f872b6c3b6d05c045385cdea3d1b702906a0ed930df7bcb7deac"
    note: "Saturn BIOS v1.01 (Japan), loaded for the Japan and Asia NTSC areas. The port checks the size only. The sha256 is the value upstream Mednafen 1.32.1 holds for this filename in its ss.bios_sanity table (src/ss/ss.cpp, BIOSDB)."
    source_ref: "mednafen/ss/ss.c:1845-1846 (region filename), mednafen/ss/ss.c:1867-1873 (open), mednafen/ss/ss.c:1961-1984 (size check, read), mednafen/ss/ss.c:1988 (sha256 for save states)"

  - name: "mpr-17933.bin"
    system: sega-saturn
    region: [north-america, europe, oceania, south-korea, asia-pal, brazil, latin-america]
    required: true
    size: 524288
    validation: {core: [size], upstream: [size, sha256]}
    sha256: "96e106f740ab448cf89f0dd49dfbac7fe5391cb6bd6e14ad5e3061c13330266f"
    note: "Saturn BIOS v1.00a (North America and Europe), loaded for every area other than Japan and Asia NTSC, and when no content is loaded. Disc area E maps to EU_PAL and the code has no Oceania area (disc.c:162-165). The port checks the size only. The sha256 is the value upstream Mednafen 1.32.1 holds for this filename in its ss.bios_sanity table (src/ss/ss.cpp, BIOSDB)."
    source_ref: "mednafen/ss/ss.c:1847-1848 (region filename), mednafen/ss/ss.c:1867-1873 (open), mednafen/ss/ss.c:1961-1984 (size check, read), mednafen/ss/ss.c:1988 (sha256 for save states), libretro.c:1103 (default area)"

  - name: "mpr-18811-mx.ic1"
    system: sega-saturn
    required: false
    min_size: 2097152
    validation: [size]
    note: "King of Fighters '95 ROM cart. Selected by the game table for MK-81088 and T-3101G or by the beetle_saturn_cart option. The first 0x200000 bytes are read. A shorter file installs a zeroed cart, an absent file leaves the slot empty."
    source_ref: "mednafen/settings.c:62-63 (filename), mednafen/ss/cart.c:197-216 (open), mednafen/ss/cart/rom.c:67-68 (read), mednafen/ss/db.c:90-91 (game table), libretro.c:527 (option)"

  - name: "mpr-19367-mx.ic1"
    system: sega-saturn
    required: false
    min_size: 2097152
    validation: [size]
    note: "Ultraman: Hikari no Kyojin Densetsu ROM cart. Selected by the game table for T-13308G or by the beetle_saturn_cart option. The first 0x200000 bytes are read. A shorter file installs a zeroed cart, an absent file leaves the slot empty."
    source_ref: "mednafen/settings.c:64-65 (filename), mednafen/ss/cart.c:197-216 (open), mednafen/ss/cart/rom.c:67-68 (read), mednafen/ss/db.c:92 (game table), libretro.c:529 (option)"

  - name: "epr-20091.ic8"
    system: sega-stv
    region: [japan, asia-ntsc]
    required: true
    size: [131072, 524288]
    validation: [size]
    note: "ST-V BIOS for Japan and Asia NTSC cabinets. Read from stvbios.zip when the bare file is absent."
    source_ref: "mednafen/ss/ss.c:1838-1839 (region filename), mednafen/ss/ss.c:1871-1988 (open, zip fallback, size check, read)"

  - name: "epr-17952a.ic8"
    system: sega-stv
    region: [north-america, brazil, latin-america]
    required: true
    size: [131072, 524288]
    validation: [size]
    note: "ST-V BIOS for North America and Central and South America cabinets. Read from stvbios.zip when the bare file is absent."
    source_ref: "mednafen/ss/ss.c:1840-1841 (region filename), mednafen/ss/ss.c:1871-1988 (open, zip fallback, size check, read)"

  - name: "epr-17954a.ic8"
    system: sega-stv
    region: [europe, south-korea, asia-pal]
    required: true
    size: [131072, 524288]
    validation: [size]
    note: "ST-V BIOS for every other cabinet region. Read from stvbios.zip when the bare file is absent."
    source_ref: "mednafen/ss/ss.c:1842-1843 (region filename), mednafen/ss/ss.c:1871-1988 (open, zip fallback, size check, read)"

  - name: "stvbios.zip"
    category: bios_zip
    system: sega-stv
    required: false
    description: "ST-V BIOS archive"
    note: "Opened only when the bare ST-V BIOS file for the cabinet region is absent. The member of the same name is matched without regard to case and must be 131072 or 524288 bytes. No hash is checked."
    source_ref: "mednafen/ss/ss.c:1888-1941 (open, member lookup, size check, extract), zip_reader.c:358-365 (case-insensitive lookup)"
    contents:
      - name: "epr-20091.ic8"
        description: "Japan and Asia NTSC"
      - name: "epr-17952a.ic8"
        description: "North America and Central and South America"
      - name: "epr-17954a.ic8"
        description: "Europe and every other region"

  - name: "mpeg_card.bin"
    system: sega-saturn
    required: false
    size: 524288
    note: "Video CD Card program ROM, opened when beetle_saturn_mpeg_card is enabled. The card carries a 512 KiB mask ROM. The core keeps at most 0x80000 bytes, pads a shorter image with zeros and checks nothing else. The image is never mapped: its presence is what makes the card authenticate, and without it the card answers commands but does not authenticate."
    source_ref: "mednafen/settings.c:68-69 (filename), mednafen/ss/cdb.c:1315-1332 (open), mednafen/ss/mpeg.c:67-71 (size), mednafen/ss/mpeg.c:423-450 (read), mednafen/ss/mpeg.c:667-675 (authentication)"

  - name: "satar4mp.bin"
    system: sega-saturn
    required: false
    min_size: 262144
    validation: [size]
    note: "Action Replay 4M Plus firmware. The first 0x40000 bytes are read as big-endian words and a shorter file leaves the cart slot empty. No hash is checked. Unfinished in source (mednafen/ss/cart/ar4mp.c:22-24), needs CPU UBC emulation. Neither the beetle_saturn_cart option (libretro.c:512-530) nor the game table of mednafen/ss/db.c yields CART_AR4MP, so the case is not reached."
    source_ref: "mednafen/settings.c:66-67 (filename), mednafen/ss/cart.c:218-236 (CART_AR4MP case), mednafen/ss/cart/ar4mp.c:181 (0x40000-byte read)"