To fully appreciate the non-merged format, it helps to look at how it compares to the other two formats used in the emulation community: and Merged . 1. Split ROM Sets
Understanding these three types is crucial for MAME management:
Because parent files are duplicated across hundreds of clone files, non-merged sets consume an immense amount of hard drive space compared to other formats.
While it takes up significantly more disk space due to file duplication, the benefits for specific users are massive: Ultimate Portability: You can grab a single ZIP file (e.g., pacman.zip non merged mame rom set
Arcade hardware was historically expensive. To save money, game developers frequently reused the same arcade system boards (motherboards) for multiple games. Furthermore, single games often had multiple regional variations (US, Japan, Europe) or revisions (v1.0, v1.1) to fix bugs.
Backing up a 100GB ROM folder takes twice as long as a 35GB folder. Copying to a portable drive or syncing to the cloud becomes cumbersome.
It is not efficient for smaller storage devices (like SD cards for Raspberry Pi). Non-Merged vs. Merged vs. Split: What’s the Difference? To fully appreciate the non-merged format, it helps
With hard drive prices plummeting (a 4TB drive costs ~$80-100 as of 2025), the storage argument for Split sets weakens every year. Meanwhile, the convenience argument for Non-Merged strengthens.
If your storage fills up, a ROM manager can convert your non-merged set back into a split or merged set seamlessly. Summary: Is a Non-Merged Set Right For You?
Unless a ROM was specifically repacked by a third party, a Non-Merged set still requires neogeo.zip , pgm.zip , or qsound.zip in your ROM folder. The game ROM contains game code; the BIOS ROM contains system-level boot code. While it takes up significantly more disk space
If a game fails to load in a split set, you must audit the ROM to find out if the error lies in the clone zip or the parent zip. With a non-merged file, if the game does not work, you know the issue is confined strictly to that single archive. The Storage Trade-Off
Every single game file is entirely standalone and self-contained.