emulator: ProSystem
type: libretro
source: "https://github.com/libretro/prosystem-libretro"
profiled_date: "2026-03-18"
core_version: "1.3e"
display_name: "Atari - 7800 (ProSystem)"
cores:
  - prosystem
systems:
  - atari-7800

notes: |
  ProSystem is an Atari 7800 emulator ported to libretro.

  BIOS loading is in core/libretro.c:579-588. Region is read from the
  cartridge header byte 57 (core/Cartridge.c:214) or overridden by the
  internal database (core/Database.c). PAL carts get the (E) BIOS,
  everything else gets (U).

  Both BIOS files are optional. The core runs games without them, but
  some titles may have compatibility issues without the real BIOS
  (startup encryption check, etc). bios_Store() maps the BIOS data
  into the top of the 64K address space (65536 - bios_size).

  No core option controls BIOS loading -- if the file exists in the
  system directory, it is loaded automatically.

files:
  - name: "7800 BIOS (U).rom"
    system: atari-7800
    required: false
    hle_fallback: true
    size: 4096  # 4 KB
    note: "NTSC/US Atari 7800 BIOS. Loaded when cartridge_region != REGION_PAL."
    source_ref: "core/libretro.c:585"

  - name: "7800 BIOS (E).rom"
    system: atari-7800
    required: false
    hle_fallback: true
    size: 16384  # 16 KB (PAL BIOS is larger than NTSC)
    note: "PAL/EU Atari 7800 BIOS. Loaded when cartridge_region == REGION_PAL."
    source_ref: "core/libretro.c:583"

platform_details:
  bios_mapping:
    target: "top of 64K memory (65536 - bios_size)"
    source_ref: "core/Bios.c:88"
    notes: |
      bios_Store() writes the BIOS into ROM at address (65536 - bios_size).
      The BIOS size is read dynamically from the file, not hardcoded.
      bios_enabled flag is set only if bios_Load() succeeds (file found
      and read without error).

  region_detection:
    source_ref: "core/Cartridge.c:214, core/Database.c"
    notes: |
      Region byte is at offset 57 in the A7800 cartridge header.
      The internal database (Database.c) can override the header value.
      REGION_NTSC = 0, REGION_PAL = 1 (defined in Region.h).