v2026.04.02/emulators/a5200.yml

emulator: a5200
type: libretro
core_classification: community_fork
source: "https://github.com/libretro/a5200"
upstream: "https://github.com/alekmaul/a5200"
profiled_date: "2026-03-22"
core_version: "2.0.2"
display_name: "Atari - 5200 (a5200)"
cores:
  - a5200
systems:
  - atari-5200

# Dedicated Atari 5200 emulator forked from Atari800 2.0.2 codebase by Alekmaul
# for GCW Zero. Libretro port later enhanced by wavemotion-dave with Altirra OS
# fallback, Super Cart support, frame blending and analog input.
#
# Loads 5200 OS ROM from <system_dir>/5200.rom (2048 bytes, mapped to 0xF800-0xFFFF
# via MEMORY_InitialiseMachine). If missing or user selects "internal" via core
# option "a5200_bios", falls back to built-in Altirra 5200 OS (altirra_5200_os.c,
# compiled from Altirra-3.20-test4).
#
# BIOS loading (libretro.c:408-499):
#   1. check_bios_variable() reads core option "a5200_bios" (official/internal)
#   2. load_bios() reads <system_dir>/5200.rom, validates size == 0x800
#   3. On failure or "internal" selected: memcpy from ROM_altirra_5200_os
#
# Upstream divergence: alekmaul's standalone requires 5200.rom (exits on missing).
# Libretro port makes it optional via Altirra fallback.
#
# Cart type detection via MD5 database in cartridge.c (standard 4K-512K, bounty bob,
# super cart, EE banked). Unknown ROMs detected by size heuristic.

files:
  - name: "5200.rom"
    path: "5200.rom"
    size: 2048
    required: false
    hle_fallback: true
    validation: [size]
    note: >
      Atari 5200 OS ROM. Core option "a5200_bios" controls official vs internal.
      Altirra replacement has lower compatibility with some titles.
    source_ref: "libretro/libretro.c:58-59, libretro/libretro.c:408-499, emu/memory.c:46"