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# JollyCV - RetroBIOS

Type | libretro
Classification | official_port
Source | https://github.com/libretro/jollycv
Upstream | https://gitlab.com/jgemu/jollycv
Version | 2.0.0
Profiled | 2026-03-24
Cores | jollycv
Systems | colecovision, creativision, myvision

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.

Technical 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.

2 files | 2 required, 0 optional | 2 in repo, 0 missing

`coleco.rom` -required

- System: colecovision
- Size: 8.0 KB
- Validation: size
- Source: `libretro/libretro.c:701, src/jcv_coleco.c:402-406`
- Platforms: lakka, recalbox, retroarch, retrobat, retrodeck, retropie
- Mapped at 0x0000-0x1FFF. Replaced by SGM lower RAM when Super Game Module is active. Must be exactly 8192 bytes.

`bioscv.rom` -required : VTech CreatiVision BIOS ROM

- System: creativision
- Size: 2.0 KB
- Validation: size
- Source: `libretro/libretro.c:711, src/jcv_crvision.c:315-318`
- Platforms: lakka, retroarch, retropie
- Mapped at 0xF800-0xFFFF. Must be exactly 2048 bytes.

Generated on 2026-03-25T14:56:43Z