934 of the 1,563 mame.yml entries named no system and so served every
system of the profile: each MAME-run system's set was the whole profile.
The 65 BIOS root sets written by hand take the system groovymame.yml
gives the same 0.289 archive (sega-systemsp, konami-gx, taito-gnet and
41 more ids, added to systems:). The 19 XaviX sets take tvgames, the
directory MAME keeps xavix.cpp in. They seed the device walk.
mame_hash_scraper --devices files a device set under arcade when a
machine no entry places loads it: MAME starts such a machine from its
set name, as an arcade folder passes it. 1,106 of the 1,254 device sets
now carry arcade, alone or beside the systems of their placed machines.
qsound, ym2413 and ym2608, written by hand, take the same answer.
Left without a system: 41 device sets no machine of the listxml
instantiates (a software list slot selects them), and the hash/,
plugins/ and floppy/ trees every machine reads.
The -listxml names the software lists each machine and slot card
declares and the floppy drives it can instantiate. --devices now writes
one entry per hash/<list>.xml the release ships under the systems of its
placed machines (111 lists, 666 stay with hash/), and files each floppy
sample under the systems whose drives select its form factor
(floppy.cpp:1428-1473, 1759-1767).
Machines a registered platform declares under one of the profile's
systems seed the walk too: bbcb, cdimono1, cdimono2, dragon32, ep64 and
ep128. Unplaced device sets go from 903 to 861.
The -listxml names, for every machine, its parent (romof), the devices of its default configuration (device_ref) and the cards its slots offer (slotoption). A machine takes the system of the first set on its romof chain a written entry lists, and passes it to each device it can instantiate. A device set reached from one system gets system:, from several the new per-entry systems:, from none neither, and keeps serving every system of the profile. The gap report, the core extras and slots read the entry's own systems, so generate_pack --system and the installer pick by them.
A machine that instantiates a device loads the device's ROMs from <shortname>.zip (src/emu/device.cpp:140-152), and a missing required ROM stops that machine (romload.cpp:529-570, 667-671). The BIOS root scan never sees these sets. mame_hash_scraper --devices --listxml reads them from the -listxml of the release mame.yml pins, refuses another release, and cites each set at the ROM_START block holding its ROMs. The BIOS root merge also wrote refs without the upstream prefix and would have rewritten all 171 of them in mame.yml.
Abdessamad Derraz