emulator: Genesis Plus GX Expanded
type: libretro
core_classification: enhanced_fork
source: "https://github.com/BillyTimeGames/Genesis-Plus-GX-Expanded-Rom-Size"
upstream: "https://github.com/ekeeke/Genesis-Plus-GX"
profiled_date: "2026-10-20"
source_commit: "dea3528cc0e3f54098e1fb91e3ae7e0e5d90a590"
upstream_commit: "e366ca817f5b750ad06a8e2c5976d79b3758ea0a"
core_version: "v1.7.4"
display_name: "Sega - MS/GG/MD/CD (Genesis Plus GX Expanded)"
cores:
  - genesis_plus_gx_expanded
  - genesisplusgx-expanded
built_by:
  - batocera
  - retrobat
systems:
  - sega-megadrive
  - sega-megacd
  - sega-mastersystem
  - sega-gamegear
  - sega-sg1000
  - sega-pico

notes: |
  Fork of Genesis Plus GX branched from ekeeke's tree at e366ca8 (May 2022).
  Makefile.libretro builds it with MAXROMSIZE 93554432 for Sega Channel
  dumps and large hacks, and it adds a Paprium mapper (core/cart_hw/paprium.h).
  RapidEdwin08/Genesis-Plus-GX-Expanded-Rom-Size, which Batocera builds as
  genesisplusgx-expanded at 181e8f93, carries the same core/, libretro/ and
  Makefile.libretro as this pin. RetroBat ships genesis_plus_gx_expanded_libretro.dll
  from its own core repository, and its strings carry the same file names and
  the Paprium track list.

  The system files are those of the mainline core, under the same names and
  read the same way: fill_pathname_join builds all twelve paths from the
  system directory (libretro/libretro.c:3581-3592). The Mega CD boot ROM of the
  disc's region is required, the Master System, Game Gear and Mega Drive boot
  ROMs are read only with the genesis_plus_gx_bios option, and the lock-on
  ROMs only with the matching lock-on cartridge.

  The Paprium mapper streams its music from a paprium folder next to the
  game, MP3 tracks named after the soundtrack (core/cart_hw/paprium.h:158-261).
  Those belong to the game release. The paprium.wav reader sits under if(0)
  (core/cart_hw/paprium.h:2748-2760) and never runs.

files:
  - name: bios_CD_U.bin
    system: sega-megacd
    region: [north-america, latin-america]
    required: true
    note: "Sega CD (NTSC-U) boot ROM. Loaded for REGION_USA, which get_region sets for every disc whose security byte at 0x20b is neither 0x64 nor 0xa1 (core/loadrom.c:1056-1070)."
    source_ref: "source core/loadrom.c:408"

  - name: bios_CD_E.bin
    system: sega-megacd
    region: [europe, oceania]
    required: true
    note: "Mega CD (PAL) boot ROM. Loaded for REGION_EUROPE, set by security byte 0x64 (core/loadrom.c:1059-1061)."
    source_ref: "source core/loadrom.c:411"

  - name: bios_CD_J.bin
    system: sega-megacd
    region: [japan]
    required: true
    note: "Mega CD (NTSC-J) boot ROM. Loaded for every other region code."
    source_ref: "source core/loadrom.c:414"

  - name: bios_U.sms
    system: sega-mastersystem
    region: [north-america, europe]
    required: false
    note: "Master System (NTSC-U) boot ROM, loaded for REGION_USA when the bios option is on."
    source_ref: "source core/loadrom.c:510"

  - name: bios_E.sms
    system: sega-mastersystem
    required: false
    note: "Master System (PAL) boot ROM, loaded for REGION_EUROPE when the bios option is on."
    source_ref: "source core/loadrom.c:513"

  - name: bios_J.sms
    system: sega-mastersystem
    region: [japan]
    required: false
    note: "Master System (NTSC-J) boot ROM, loaded for the Japanese region codes when the bios option is on."
    source_ref: "source core/loadrom.c:516"

  - name: bios.gg
    system: sega-gamegear
    required: false
    note: "Game Gear boot ROM, 1 KB Majesco image or a larger one, loaded when the bios option is on."
    source_ref: "source core/loadrom.c:479"

  - name: bios_MD.bin
    system: sega-megadrive
    required: false
    note: "Mega Drive TMSS boot ROM. 2 KB read, accepted when \"GENESIS OS\" sits at 0x120."
    source_ref: "source libretro/libretro.c:3713-3721"

  - name: ggenie.bin
    system: sega-megadrive
    required: false
    note: "Game Genie ROM, read when the Game Genie lock-on is selected."
    source_ref: "source core/cart_hw/ggenie.c:64, source libretro/libretro.c:3581"

  - name: areplay.bin
    system: sega-megadrive
    required: false
    note: "Action Replay (Pro) ROM, read when the Action Replay lock-on is selected."
    source_ref: "source core/cart_hw/areplay.c:64, source libretro/libretro.c:3582"

  - name: sk.bin
    system: sega-megadrive
    required: false
    size: 2097152
    validation: [size]
    note: "Sonic & Knuckles ROM for the lock-on cartridge, kept only when the read fills 2 MB."
    source_ref: "source core/cart_hw/md_cart.c:762"

  - name: sk2chip.bin
    system: sega-megadrive
    required: false
    size: 262144
    validation: [size]
    note: "Sonic & Knuckles UPMEM ROM, read after sk.bin and kept only when the read fills 256 KB."
    source_ref: "source core/cart_hw/md_cart.c:768"