Unlike Split or Merged sets, Non-Merged sets do rely on a parent-child relationship at the file system level. MAME does not need to reference a parent zip to locate shared ROM data. Every required byte for a given game resides within its own archive.
It is the simplest format for users who want to curate a small, specific list of games rather than keeping a massive library of thousands of titles. LaunchBox Community Forums The Downsides About ROMs and Sets - MAME Documentation
However, if storage is a concern, or if you prefer a more consolidated collection where some files are shared among games (which can reduce overall size), a Merged ROM set might be more suitable.
The Ultimate Guide to Non-Merged MAME ROM Sets: Structure, Advantages, and Setup
Best for users who only want to pick 50–100 specific titles for a handheld or a custom arcade cabinet. When Should You Use This? non merged mame rom set
To understand a non-merged set, you must first understand how MAME handles arcade hardware.
Even in a non-merged set, there is one crucial rule to remember:
: You can delete 90% of the ROM set to save space without breaking the 10% you want to keep. In a split set, deleting the "parent" game would break all its clones.
Every zip file is an island. The parent is separate, and every individual clone has its own separate zip containing 100% of the data needed to run the game. The Massive Advantages of Non-Merged Sets Unlike Split or Merged sets, Non-Merged sets do
If you are diving into the world of arcade emulation, you will quickly encounter MAME (Multiple Arcade Machine Emulator). While MAME is the gold standard for preserving arcade history, its ROM organization system can be highly confusing for beginners.
: A popular front-end that includes a "MAME Full Set Importer," which can help filter out clones, mechanical games, or non-working titles during the import process. ⚖️ Final Verdict: Is it for you? Recommended Set "I want every game ever made and have limited HDD space."
The independent nature of a non-merged set is the key to understanding its strengths and weaknesses.
The Multiple Arcade Machine Emulator (MAME) project utilizes complex ROM management structures to handle thousands of arcade boards, clones, and revisions. Among the three primary ROM set formats—Split, Merged, and Non-Merged—the Non-Merged set offers a unique approach to file organization. This paper provides a comprehensive examination of the Non-Merged MAME ROM set, detailing its file structure, storage efficiency, practical benefits, and drawbacks compared to other formats. The analysis concludes that while the Non-Merged set is the least space-efficient, it offers superior simplicity for end-users, especially those managing small collections or performing manual ROM audits. It is the simplest format for users who
Common files (e.g., sound CPU ROMs, graphics tiles) are duplicated across clones — meaning storage size approximates (sum of all unique roms) + (sum of all shared roms × clone_count) .
Modern frontends like LaunchBox, RetroPie, Batocera, and CoinOPS rely on clean game lists. Non-merged sets prevent duplication errors and simplify the scraping of box art, video previews, and metadata. Simpler Troubleshooting
: It is the preferred format for "stripping down" a full MAME set. You can use tools like the MAME Smart ROM Sorter