Games & Preservation

Backing Up Atari 7800 Games

A useful Atari 7800 backup contains both the cartridge bytes and a small description of the board hardware needed to run them. That metadata lives in the .a78 header. A current Open Source Cartridge Reader writes the format directly, making preservation much less error-prone than the old raw-dump workflow. Start with the legal ground rules: own it, dump it yourself, keep it private.

Media
Atari 7800 cartridge.
Hardware
OSCR with the Atari 7800 adapter.
Output
Headered .a78 image.
Typical size
16–144 KB for most commercial releases.
Save data
No standard battery-backed save system in the original library.
BIOS
Optional to the core; OWL does not require one.
Atari 7800 console with joystick controller
The North American Atari 7800 with its joystick controller. Image: Evan-Amos, CC BY-SA 3.0, via Wikimedia Commons.

What You Need

  • An Open Source Cartridge Reader with the custom Atari 7800 adapter.
  • A microSD card and a current OSCR database/firmware release; 7800 support continues to receive mapper and title updates.
  • Cleaning supplies and the original cartridge you own.

Dumping, Step by Step

7800 cartridgeROM + board hardware1OSCR identifies boardmapper, audio, controllers2Game.a78128-byte header + ROM3verify twice → archive → OWL
The A78 header records facts the raw ROM does not: how the cartridge maps memory and which extra hardware it contains. Diagram: NDEVR.
  1. Update the reader database, then connect the 7800 adapter with power removed.
  2. Clean and insert the cartridge; choose Atari 7800 and confirm the detected title or board type.
  3. Dump twice and compare the full file hashes.
  4. Archive the resulting .a78 file without stripping its header.

Unlike a 2600 .a26 rename, converting a raw 7800 .bin into .a78 is not merely changing the extension. The A78 format prepends a 128-byte header describing the title, cartridge type, mapper, audio hardware, region, and controller expectations. Wrong metadata can make a perfect ROM dump boot incorrectly.

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Prefer the reader’s headered output

If your tool produces only a raw binary, preserve it untouched and create a separate .a78 copy with a dedicated A78 header utility and verified database metadata. Do not invent settings from file size alone.

The 7800 is also backward-compatible with most 2600 cartridges, but the cartridge itself determines the backup format: dump a 2600 game as .a26 and a 7800 game as .a78.

Playing Your Backup

Upload Game.a78 to your OWL media library. OWL recognizes Atari 7800 automatically and launches EmulatorJS’s ProSystem core with native two-button, pause, reset, select, and difficulty-switch bindings.