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[fleggett]

Okay, so you've amassed this huge collection of roms from various sources.  We're talking gigs and gigs of files.   You're very proud of your due diligence in keeping current with the mame scene.

And then - B A M - a new version of mame appears.  You think great, now some of my unplayable roms might now at least somewhat work.

But then it happens - a tremendous amount of VERSION-SPECIFIC roms start flooding the scene.  And you get a nasty surprise.  Roms that worked before (at least, to some degree), don't work now with the new mame executable.  You internally sigh, download the batch, and run something like cmpro.  It's a classical rinse and repeat.

My question is - why is this a necessity?  If a rom ran just fine 10 versions back, why would it suddenly stop running when the latest and greatest mame executable comes onto the scene.  Why are roms being altered in the first place?  Because they were incorrectly or incompletely dumped?  If that was the case, then I'd think they wouldn't run at all, no matter what version of mame is being used at the time.

Is a rom ever "perfected" to the point that it needs no further cmpro-type processing?  Can these 100% working roms be quarantined in some fashion?  Or is the scene plagued by roms upon roms upon roms that, for whatever reason, are broken or incomplete in some way.

This is something that's always mystified me.  I would think that, great, a new version of mame has come out.  And those roms which didn't work before (but do now) get posted.  I do NOT understand why these mega-floods happen, as I just can't believe each and every one of the previous rom versions were broken in some way.

Is there a "perfect" set of roms (and CHDs) that exist out there, somewhere?  Is that even possible given the current mame development cycle?

Sorry for being long-winded.  I also realize I asked a lot more than just one question.  Thanks in advance!

[Roman]

Well....easy answer:
There are no (or at least nearly no) perfect romsets.

If a game is dumped for the first time it migh:

- lack correct naming of the files (MAME devs prefer the chip labels as filenames)
- the dump of one or more ICs are bad (overdumped, missed the half, bit flips etc...)
- some chips were not dumped (e.g. because the dumper didn't have equipment to dump special chips)
- PALs/GALs/EEPROMs were not dumped
- MCUs were not dumped

You can group such (and there are more) issues in

- the game is playable
- the game is not playable (but MAME is a documentation project, so they get included)
- the game is partly playable (e.g. it runs but due to a damaged gfx rom you see bad gfx)
- the game is playable but things like encryption is solved via some hacks and not by emulating e.g. the MCU which handles it in reality.

Soooo....even if a set seems to be playable for the end user it can be "NOT PERFECT" from the MAME dev point of view...

Typical changes if a new version of MAME is out are:

- correcting the romnames
- correcting the parent/clone relationships
- adding dumped ICs which weren't dumped yet
- replacing bad dumps
- changing byte ordering
- adding newly found bios roms (e.g. for different regions) to bios sets
- etc...

For CHDs, there were some changes in the past but they were mainly based on updating the CHD format itself to a new version (which e.g. supports hashing of metadata etc..)

[fleggett]

My (belated) thanks for the explanation.  You should sticky this in some way.  I can't believe I'm the only person who didn't understand this, though the concept of of a "badly dumped" ROM just seems a little bizarre in this day and age.

And, apparently, there are a LOT of "not 100%" ROMs currently in the wild, as every time there's even a minor MAME release, there's a subsequent flood of new ROMs to go along with that release.

[Roman]

Well...that's MAME