In MAME, many games are "clones" (variants) of a "parent" (the main version). Usually, clones rely on the parent ROMs to function.
Disclaimer: This article does not condone piracy. You must own original arcade PCBs to legally use ROMs. This information is for educational purposes regarding file structures.
In MAME (Multiple Arcade Machine Emulator), a Non-Merged ROM set is a collection where every game’s ZIP file contains all the files necessary to run that specific game by itself, including files that would otherwise be shared with other games (like parent ROMs, device ROMs, and BIOS files). non merged mame rom set
Think of it as a "self-contained" set. If you download Street Fighter II from a non-merged set, that single ZIP file will run immediately, regardless of what other ROMs you have.
| Use Case | Recommended? | | :--- | :--- | | You only want 10-20 specific games | ✅ Yes – just download those non-merged ROMs | | You’re setting up a RetroPie / Batocera | ✅ Yes – avoids BIOS/parent lookup issues | | You have plenty of disk space | ✅ Yes – simplest to manage | | You want a complete MAME collection | ❌ No – use split or merged to save space | | You regularly update MAME | ❌ No – split sets are easier to update | In MAME, many games are "clones" (variants) of
To understand Non-Merged, you must know the two other main MAME set types:
| Feature | Non-Merged | Split | Merged | | :--- | :--- | :--- | :--- | | Parent ROM (e.g., sf2.zip) | Contains all files (parent + child + BIOS) | Contains only parent’s unique files | Contains all files for parent + ALL children | | Child/Clone ROM (e.g., sf2ce.zip) | Contains all files needed to run (parent + clone differences + BIOS) | Contains only the difference files (requires parent) | Nothing separate (files are inside parent) | | BIOS files (e.g., neogeo.zip) | Included inside each game’s ZIP | Separate ZIP file required | Separate ZIP file required | | File Size | Largest | Medium | Smallest (for storage) | | Ease of Use | Easiest (no dependencies) | Medium (requires parent/BIOS) | Complex (hard to extract single game) | | Use Case | Recommended
The Non-Merged MAME ROM set is not superior or inferior to Split; it is different by design for a different user.
Ultimately, the best MAME experience is the one that gets you playing games faster. For many, that’s Non-Merged. For purists, it’s Split. But never use Fully Merged unless you enjoy pain.
Now, go play Galaga. And remember: the ROM structure doesn’t matter if you’re having fun.
Because of the redundancy, downloading a full Non-Merged set consumes more bandwidth. Updating from version 0.250 to 0.251 requires downloading larger patch files or more changed archives.