emulator: Gearlynx
type: libretro
core_classification: official_port
source: "https://github.com/drhelius/Gearlynx"
profiled_date: "2026-03-21"
core_version: "1.0.0"
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 at
  retro_load_game time (libretro.cpp:106-130, function load_bootroms).
  Path is built as: system_directory + "/lynxboot.img", no subdirectory.

  LoadBios in media.cpp:274 reads exactly 512 bytes (GLYNX_BIOS_SIZE
  = 0x200, 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,
  game_db.h:38). 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
  gearlynx_core_inline.h:31-37 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
  Core options: none documented in the libretro port.

files:
  - name: "lynxboot.img"
    description: "Atari Lynx boot ROM"
    region: "World"
    required: true
    size: 512
    sha1: "e4ed47fae31693e016b081c6bda48da5b70d7ccb"
    md5: "fcd403db69f54290b51035d82f835e7b"
    crc32: "0d973c9d"
    source_ref: "libretro.cpp:106-130 (load_bootroms), media.cpp:274-329 (LoadBios), defines.h:52 (GLYNX_BIOS_SIZE=0x200), game_db.h:38 (GLYNX_DB_BIOS_CRC=0x0D973C9D), gearlynx_core_inline.h:33-37 (no-bios guard)"
    notes: "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)."