emulator: JollyCV
type: libretro
core_classification: official_port
source: "https://github.com/libretro/jollycv"
upstream: "https://gitlab.com/jgemu/jollycv"
profiled_date: "2026-09-17"
source_commit: "2790d59c7194d29e83f8603ffd7e9da17f11575e"
upstream_commit: "18875ffdb1891cec04217cf02928af563a3af9d8"
core_version: "2.1.0"
display_name: "ColecoVision/CreatiVision/My Vision (JollyCV)"
cores:
  - jollycv
systems:
  - colecovision
  - creativision
  - myvision

notes: |
  JollyCV emulates the ColecoVision (with Super Game Module), the VTech
  CreatiVision and the Nichibutsu My Vision. The libretro port and the
  Jolly Good build share the same src/ tree, and only the front end differs.

  The libretro port picks the system from the file name
  (libretro/libretro.c:670-679): ".myv" is My Vision, ".rom" and ".bin"
  are looked up by MD5 in the CreatiVision table (src/jcv_db.c:109-176,
  reached through src/jollycv.c:118-120) and fall back to ColecoVision,
  ".col" is ColecoVision. A CreatiVision image whose MD5 is not in the
  table runs as ColecoVision. Version 2.1.0 moved that table from
  libretro/gamedb.h into src/jcv_db.c so both builds share it.

  BIOS files are read from the front end's system directory, no
  subdirectory, as "<system_dir>/coleco.rom" or "<system_dir>/bioscv.rom"
  (libretro/libretro.c:696-716). jcv_bios_load_file (src/jollycv.c:406-432)
  opens the file, reads it whole and hands the buffer to
  jcv_coleco_bios_load or jcv_crvision_bios_load, which keep it only when
  the size is exactly SIZE_CVBIOS (8192) or SIZE_CRVBIOS (2048). The return
  value of that size check is dropped at src/jollycv.c:427, so a file of the
  wrong size passes the loader while the BIOS pointer stays NULL, and the first
  BIOS read (src/jcv_coleco.c:281-282, src/jcv_crvision.c:443-444) then
  dereferences it. A missing file fails retro_load_game. My Vision loads no
  BIOS (libretro/libretro.c:717-719).

  The Jolly Good build reads the same two names from the front end's BIOS
  path (jg.c:463-481) and declares them through jg_get_bioslist with an
  MD5 each (jg.c:151-156). The core never compares those MD5. The reference
  front end hashes the file against them for a debug log only
  (jgrf src/jgrf.c:441-458). The md5: fields below carry these values.

  ColecoVision cartridges start with 0xAA55 to show the BIOS title screen or
  0x55AA to jump straight to the game vector (src/jcv_coleco.c:421-426).
  The MD5 database of ColecoVision games in src/jcv_db.c selects cartridge
  mappers and controller flags.

files:
  - name: "coleco.rom"
    system: colecovision
    description: "ColecoVision BIOS"
    required: true
    size: 8192
    md5: "2c66f5911e5b42b8ebe113403548eee7"
    validation: [size]
    source_ref: "libretro/libretro.c:697-703, src/jollycv.c:406-432, src/jcv_coleco.c:402-410, jg.c:151-153"
    note: "Mapped at 0x0000-0x1FFF, replaced by the lower 8K of SGM RAM when the Super Game Module enables it. The MD5 is the value the JG bioslist declares, and the core compares the size only."

  - name: "bioscv.rom"
    system: creativision
    description: "VTech CreatiVision BIOS ROM"
    required: true
    size: 2048
    md5: "3b1ef759d8e3fb4071582efd33dd05f9"
    validation: [size]
    source_ref: "libretro/libretro.c:707-713, src/jollycv.c:406-432, src/jcv_crvision.c:316-324, jg.c:154-155"
    note: "Mapped at 0xF800-0xFFFF. The MD5 is the value the JG bioslist declares, and the core compares the size only."

platform_details:
  colecovision:
    bios_filename: "coleco.rom"
    bios_size: 8192
    memory_map: "0x0000-0x1FFF"
    source_ref: "src/jcv_coleco.c:268-283"

  creativision:
    bios_filename: "bioscv.rom"
    bios_size: 2048
    memory_map: "0xF800-0xFFFF"
    source_ref: "src/jcv_crvision.c:316-318, 443-445"

  myvision:
    bios_required: false
    source_ref: "libretro/libretro.c:717-719"
    note: "No BIOS is loaded for My Vision."