emulator: Gearlynx
type: libretro
core_classification: official_port
source: "https://github.com/drhelius/Gearlynx"
profiled_date: "2026-10-04"
source_commit: "6a939afbca387ca615d96433928866e9d16ba2de"
core_version: "1.2.33"
display_name: "Atari - Lynx (GearLynx)"
cores: [gearlynx]
systems: [atari-lynx]
verification: existence

notes: |
  Gearlynx is an Atari Lynx emulator by Ignacio Sanchez (drhelius).
  The libretro core loads lynxboot.img from the system directory in
  retro_load_game() and again in retro_reset()
  (platforms/libretro/libretro.cpp:170-212, function load_bootroms).
  Path is built as: system_directory + "/lynxboot.img", no subdirectory.
  With the libretro VFS the file is read by load_bios_file() and handed to
  LoadBiosFromBuffer(), otherwise Media::LoadBios() opens it
  (platforms/libretro/libretro.cpp:130-168, src/media.cpp:578-620).

  LoadBiosData in src/media.cpp:633-683 takes exactly 512 bytes
  (GLYNX_BIOS_SIZE = 0x200, src/defines.h:52). If the file size is not
  0x200, the load is rejected with BIOS_LOAD_INVALID_SIZE. After loading,
  bytes at offset 0x1F8 and 0x1F9 are patched (RAM/MAPCTL registers), then
  CRC32 is computed and compared against GLYNX_DB_BIOS_CRC (0x0D973C9D,
  src/game_db.h:47). An invalid CRC triggers a warning log but the BIOS
  is still marked as loaded (m_is_bios_loaded = true).

  No HLE fallback. If the BIOS is not loaded (IsBiosLoaded() returns
  false), RunToVBlank in src/gearlynx_core.cpp:216-221 renders a static
  "no bios" image and returns false, refusing to emulate. The BIOS is
  required for any ROM to run. Homebrew (.o, BS93 format) bypasses the
  normal boot sequence via PrepareForHomebrew() but still requires the
  BIOS to be loaded for the emulation loop to execute.

  ROM extensions: .lnx, .lyx, .o, .bin

files:
  - name: "lynxboot.img"
    description: "Atari Lynx boot ROM"
    required: true
    size: 512
    crc32: "0d973c9d"
    validation: [size, crc32]
    source_ref: "platforms/libretro/libretro.cpp:170-212 (load_bootroms), src/media.cpp:633-683 (LoadBiosData), src/defines.h:52 (GLYNX_BIOS_SIZE=0x200), src/game_db.h:47 (GLYNX_DB_BIOS_CRC=0x0D973C9D), src/gearlynx_core.cpp:216-221 (no-bios guard)"
    note: "512-byte boot ROM validated by CRC32 after load. Invalid CRC logs a warning but still works. Missing or wrong-size file blocks emulation entirely (no HLE fallback)."