emulator: Handy
type: libretro
core_classification: community_fork
source: "https://github.com/libretro/libretro-handy"
upstream: "https://handy.sourceforge.net/"
profiled_date: "2026-03-23"
core_version: "0.95"
display_name: "Atari - Lynx (Handy)"
cores:
  - handy
systems: [atari-lynx]

notes: |
  Handy is an Atari Lynx emulator by K. Wilkins (Handy 0.95, 2007).
  The core loads lynxboot.img from the system directory and validates
  it by CRC32 (0x0D973C9D). If the file is missing or the CRC does
  not match, the core falls back to an internal HLE BIOS that
  replicates the boot sequence in software (ram clear, cart loader
  decrypt, jump to $0200).

  The HLE path intercepts CPU calls to ROM addresses FE00, FE19, FE4A
  and FF80 via a Mikie register write trap (address 0xFD97). When
  useEmu is true (no valid BIOS loaded), CRom initialises mRomData
  with a default fill byte (0x88) plus reset vectors pointing to
  the HLE entry points.

  Upstream Handy 0.95 requires the BIOS (throws CLynxException) and
  validates by checking the first 16 bytes against a hardcoded
  signature. The libretro port added the HLE fallback and switched
  to full CRC32 validation.

  For headerless cartridges (no LNX/BS93 header), the core loads
  howard.o from the system directory. This is the Epyx development
  kit bootloader used to bootstrap raw/headerless ROMs into memory.
  Upstream requires howard.o for headerless carts (throws exception);
  the libretro port makes it optional (logs error, continues).

files:
  - name: "lynxboot.img"
    system: atari-lynx
    description: "Atari Lynx boot ROM (Mikie internal 512B ROM)"
    required: false
    hle_fallback: true
    size: 512
    crc32: "0d973c9d"
    validation: [size, crc32]
    source_ref: "rom.h:48-49 (ROM_SIZE=0x200, ROM_CRC32=0x0D973C9D), rom.cpp:76-129 (CRom constructor), libretro.cpp:1231-1258 (bios path + CSystem init)"
    note: "Validated by CRC32 at load time. If invalid or missing, core uses HLE fallback (system.cpp:303-361 HLE_BIOS_* functions, system.cpp:406-428 trap writes)."

  - name: "howard.o"
    system: atari-lynx
    description: "Epyx Howard bootloader for headerless cartridges"
    required: false
    source_ref: "system.cpp:197-238 (CartHeaderLess check, howard.o load via fill_pathname_resolve_relative)"
    note: "Loaded only for headerless carts (no LNX/BS93 header). Resolved relative to the BIOS file path (system directory). Passed to CRam for execution. Most commercial games have headers and skip this entirely."