emulator: JollyCV
type: libretro
core_classification: official_port
source: "https://github.com/libretro/jollycv"
upstream: "https://gitlab.com/jgemu/jollycv"
profiled_date: "2026-03-24"
core_version: "2.0.0"
display_name: "ColecoVision/CreatiVision/My Vision (JollyCV)"
cores:
  - jollycv
systems:
  - colecovision
  - creativision
  - myvision

notes: |
  JollyCV is a multi-system emulator by Rupert Carmichael supporting
  ColecoVision (with Super Game Module), CreatiVision, and My Vision.

  BIOS handling depends on the detected system type (set via core option
  or auto-detected from ROM database via jcv_process_hash/jcv_get_dbflags):

  - ColecoVision (JCV_SYS_COLECO): loads "coleco.rom" from system dir.
    BIOS is mapped at 0x0000-0x1FFF. Size must be exactly 8192 bytes
    (SIZE_CVBIOS = SIZE_8K = 0x2000). Load fails if size mismatches.
    Without the BIOS, ColecoVision games will not run (load returns false).

  - CreatiVision (JCV_SYS_CRVISION): loads "bioscv.rom" from system dir.
    BIOS is mapped at 0xF800-0xFFFF. Size must be exactly 2048 bytes
    (SIZE_CRVBIOS = SIZE_2K = 0x800). Without the BIOS, CreatiVision
    games will not run.

  - My Vision (JCV_SYS_MYVISION): no BIOS required.

  The libretro port constructs paths via snprintf("%s%c%s", sysdir, pss,
  filename) in libretro.c:699-711. jcv_bios_load_file() opens the file,
  reads it fully, then delegates to jcv_coleco_bios_load() or
  jcv_crvision_bios_load() which validate size before copying.

  ColecoVision cartridge header bytes at offset 0x0000-0x0001 control
  boot behavior: 0xAA55 shows the BIOS title screen, 0x55AA jumps
  directly to the game code vector.

  The core includes a built-in ROM database with MD5 hashes (gamedb.h)
  for game-specific flags, but this is for game compatibility, not BIOS
  verification.

files:
  # --- ColecoVision BIOS (required for CV games) ---
  - name: "coleco.rom"
    system: colecovision
    required: true
    size: 8192
    validation: [size]
    source_ref: "libretro/libretro.c:701, src/jcv_coleco.c:402-406"
    notes: "Mapped at 0x0000-0x1FFF. Replaced by SGM lower RAM when Super Game Module is active. Must be exactly 8192 bytes."

  # --- CreatiVision BIOS (required for CreatiVision games) ---
  - name: "bioscv.rom"
    system: creativision
    description: "VTech CreatiVision BIOS ROM"
    required: true
    size: 2048
    validation: [size]
    source_ref: "libretro/libretro.c:711, src/jcv_crvision.c:315-318"
    notes: "Mapped at 0xF800-0xFFFF. Must be exactly 2048 bytes."

platform_details:
  colecovision:
    bios_filename: "coleco.rom"
    bios_size: 8192
    memory_map: "0x0000-0x1FFF"
    source_ref: "src/jcv_coleco.c:269-281"

  creativision:
    bios_filename: "bioscv.rom"
    bios_size: 2048
    memory_map: "0xF800-0xFFFF"
    source_ref: "src/jcv_crvision.c:315-337, 441"

  myvision:
    bios_required: false
    notes: "No BIOS needed. My Vision games run without any system ROM."