MAME Split Merged and Non-Merged Sets

From Retro Arcade Guides

Some MAME Torrents are released in up to three different flavors:


Split Set
A split set is one where the parent set contains all of the normal data it should, and the clone sets contain only what has changed as compared to the parent set. This saves some space, but isn’t quite as efficient as a merged set. The clone sets can't operate without their parent set.

Remark: The parent and clones in split sets DO NOT include BIOS or DEVICE files - they are separate files within the set (an example would be 100lions.zip, which has no BIOS in the parent; and galaga.zip, which has no device files in the parent). This is per MAME design.


Merged Set
A merged set takes the parent set and its clone sets and puts them all inside the parent set's archive. To use the existing Pac-Man example, combining the Puckman, Midway Pac-Man (USA) sets, along with various bootleg versions, and combining it all into puckman.zip (the parent's archive), would be making a merged set.

Remark: The parent games in a merged set DO NOT include BIOS or DEVICE files - they are separate files within the set (an example would be 100lions.zip, which has no BIOS in the parent; and galaga.zip, which has no device files in the parent). This is per MAME design.


Non-Merged Set
A non-merged set is one that contains absolutely everything necessary for a given game to run in one ZIP file.

Remark: Even though non-merged games normally DO NOT include BIOS or DEVICE files within the game, in the case of the Pleasuredome "Non-Merged" set we DO include these within the game, which ensures that every single game can be copied and ran as individual game without the need of any extra files. This makes a set like this ideal for splitting up on a per-game-basis.

The non-merged set is ideal for those people that work on Arcade PCBs as ALL roms/devices/bios files are contained within the game. This set is also great for those that for instance create their own arcade cabinets and want to copy only very specific games to their PC/Raspberry/Other, the game.zip file contain all the files needed, no more searching for the dependent parent files, BIOS files, device files - just copy galaga.zip and you are set.

Pick individual games from this set if you are not intending to download a complete ROM set.


Notes:

  • All MAME torrents available on Pleasuredome were created in a way that their contents can be used directly in MAME or Frontends, without the need of copying, moving, renaming, compressing, or extracting any files or folders.
  • No setting is needed to tell MAME which set type is being used. MAME always looks for files in all expected possible places.


Comparison Tables

For illustrative purposes, below is a comparison table for the "MAME ROMs" torrents:

Torrent Size
(GB)
Zip
files
Average size
per file (KB)
Split 71.17 38,200 1,953.67
Merged 68.88 13,535 5,336.00
Non-Merged 125.92 38,754 3,406.92


A comparison table for the "MAME Software List ROMs" torrents follows:

Torrent Size
(GB)
Zip
files
Average size
per file (KB)
Split 74.19 118,490 656.58
Merged 73.89 80,226 965.72


Conclusion

In short, the three set types have the same contents, but organized differently. In fact, if you have one of these torrents, the other one(s) can be created using a ROM Manager such as clrmamepro or RomVault because the contents are the same.

Note that Non-Merged is about two times larger than Split or Merged, which makes it a bad choice if the intention is to download the entire torrent (any of the smaller torrents can be downloaded to create the Non-Merged one).


See also