MAME parent, clone, BIOS, and CHD files explained as a dependency map
Treat the selected game as the root of a dependency graph. A split clone may need its parent; either may need a separate BIOS or device set; a CHD game needs its correctly named CHD in the expected folder; and a delta CHD also needs its parent CHD.
Do this in order
- 01
Identify the exact game short name and whether MAME labels it a clone.
- 02
Determine whether your set is split, non-merged, full non-merged, or merged.
- 03
List the parent and BIOS/device relationships reported by the target version.
- 04
For disk-based games, place the CHD unzipped in the folder structure expected by MAME.
- 05
Run the targeted ROM audit, then validate CHD presence and parent linkage.
- 06
Change only one dependency at a time and preserve your known-good backup.
Decision and diagnostic table
| Object | Contains | May depend on |
|---|---|---|
| Clone set | Data that differs from a related parent | Parent and possibly BIOS/device set |
| BIOS/device set | Shared platform firmware or device data | Its own version-specific definition |
| CHD | Compressed disk, optical, or other mass-storage image | Matching game folder; delta may require parent CHD |
| Full non-merged set | Game plus parent and BIOS ROM data in one archive | CHD files can still remain separate |
Split and non-merged answer different storage goals
A split collection avoids duplicating shared ROM data, so a clone archive is intentionally incomplete without its parent and BIOS sets. A non-merged game can include parent data, while a full non-merged set can also include BIOS ROM data. These labels describe packaging, not permission.
Merged archives place clones inside a parent archive. They save space but can be awkward in frontends that expect a selectable archive per revision.
CHD is not another ZIP
CHD stores mass-media images and is already compressed. MAME recommends keeping CHDs out of ZIP or 7z archives. A common layout is a short-name folder beside the game archives, with the CHD inside that folder.
A correct ROM audit does not prove a required CHD is present. Read the launch message and check the file search path separately.
Use the emulator’s graph, not a download checklist
MAME reports what it expected and where it looked. That output is safer and more accurate than a generic web list because dependencies can change across releases.
When you lack a required parent, BIOS, or disk image, return to your own hardware dump or an explicitly authorized source. Do not search the filename on unreviewed download sites.
BIOS and CHD files can be copyrighted just like game ROMs. Technical necessity is not distribution permission.