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RetroBIOS

JollyCV

JollyCV emulates ColecoVision, VTech CreatiVision and Nichibutsu My Vision. It reads 2 files, 2 of them required: without a required file it does not start games. A required file is needed only by the machines that use it. Each file below cites the line of source code that reads it.

About this profile
Detail Value
Type libretro
Classification Official port
Source https://github.com/libretro/jollycv
Upstream https://gitlab.com/jgemu/jollycv
Version 2.1.0, stated in version.h
Revision libretro/jollycv@2790d59c7194, jgemu/jollycv@3caacb221435
Profiled 2026-09-17
Profile YAML, JSON
Cores jollycv
Systems ColecoVision, VTech CreatiVision, Nichibutsu My Vision
Install this emulator's files

The installer finds your setup and its BIOS folder, then downloads only the files this emulator reads there and checks each one.

Open the Start menu. Type PowerShell and open it. Paste the line. Press Enter.

PowerShell
&([scriptblock]::Create((irm https://abdess.github.io/retrobios/i.ps1))) --emulator jollycv
Platform details
Technical 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

Section titled “Files”

2 files: 2 required, 0 optional.

In this collection: 2 in repo and 0 missing.

Required

Section titled “Required”

coleco.rom required for ColecoVision in repo

ColecoVision BIOS

  • System: ColecoVision
  • 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.
  • Size: 8.0 KB, MD5 2c66f5911e5b
  • Collection copy: bios/Coleco/ColecoVision/BIOS.col
  • Platforms: BIOS.col and coleco.rom and colecovision.rom: Lakka, RetroArch, RetroPie. colecovision.rom: Batocera, EmuDeck. Coleco_Bios.bin: BizHawk. Machines/COL - ColecoVision with Opcode Memory Extension/coleco.rom and Machines/COL - ColecoVision/coleco.rom and coleco/boot.rom: Recalbox. bios/BIOS.col and bios/Machines/COL - ColecoVision with Opcode Memory Extension/coleco.rom and bios/Machines/COL - ColecoVision/coleco.rom and bios/colecovision.rom: AmberELEC. bios/BIOS.col and bios/coleco.rom and bios/colecovision.rom: RetroDECK. bios/Machines/COL - ColecoVision with Opcode Memory Extension/coleco.rom and bios/Machines/COL - ColecoVision/coleco.rom: EmuELEC. coleco.rom and colecovision.rom and openMSX/share/systemroms/coleco.rom: RetroBat. colecovision/colecovision.rom: RomM
Hashes, validation and source

bioscv.rom required for VTech CreatiVision in repo

VTech CreatiVision BIOS ROM

  • System: VTech CreatiVision
  • Mapped at 0xF800-0xFFFF. The MD5 is the value the JG bioslist declares, and the core compares the size only.
Hashes, validation and source

Next steps

Section titled “Next steps”
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Maintained by Abdess on GitHub. Report a problem.

Packs from release v2026.10.10, .

MIT for the tooling and metadata. BIOS and firmware files are third-party system software, preserved for personal backup, archival and interoperability.