Reducing MAME CHD footprint. Easiest Method?

[Avenger]

I've been loving the deep, integrated MAME support in GameEx.  I have a question not directly pertaining to the software.  I set up GameEx to show only working ROMs and also conveniently, on the category screen you can view CHD games.  I have a full Romset and it shows about 120 playable games with CHD files.  I'm setting up a portable system which will not be able to hold the 450GB or so of the complete CHD set.  Can anyone suggest the easiest way of only keeping the CHD's from the 120 working games? I guess I want to copy those files into a separate directory to put on my mini-laptop.  The most brute force way I guess would be to write them all down and figure out each file name from running the MAME executable (from the little GUI that comes up). Anybody with a better idea?

[tthurman]

This topic comes up frequently, and to my knowledge, there isn't any easy way.

Most systems struggle with CHD's to at least some degree, are you sure your portable can handle them? 

This fellow put together a fairly extensive guide doing this in RA which may work offer some insight.

 

Given the overall limited number of CHD's, respective to the ROMSET anyway, it may be easiest just to hammer through them and pitch what you don't want.  They're merged in most cases though, so make sure you don't pitch something you need.

[Avenger]

29 minutes ago, tthurman said:

This topic comes up frequently, and to my knowledge, there isn't any easy way.

Most systems struggle with CHD's to at least some degree, are you sure your portable can handle them? 

This fellow put together a fairly extensive guide doing this in RA which may work offer some insight.

 

Given the overall limited number of CHD's, respective to the ROMSET anyway, it may be easiest just to hammer through them and pitch what you don't want.  They're merged in most cases though, so make sure you don't pitch something you need.

Yes that post uses RomLister which hasn't been updated for the recent CHD formats or else it would be perfect.  When you say they are merged, are you talking about the multiple files in one CHD sub-directory?  If I have a rom file name for a game I want to keep, do I look for the same file name as a CHD sub directory name or do I have to search through the subdirectories to find the files and then keep the whole sub Directory?  What I am asking does the ROM file name directly correspond to a CHD sub directory name or can it be one of the files in a sub directory?

[tthurman]

Merged sets "borrow" from other titles in an effort to conserve disc space.  I'm really not sure how prevalent this is with CHD's though.

Merged  = Borrows multiple files from other titles  (least amount of storage space required)

Split = Less so

Non-Merged = No dependency on other titles   (most amount of storage space required)

Say NFL blitz shares a common file with NBA Jam that is located in the NBA Jam folder (which you throw out).  In a merged set scenario, NFL Blitz becomes non-working.

This is hypothetical only.

 

[Avenger]

 

4 hours ago, tthurman said:

Merged sets "borrow" from other titles in an effort to conserve disc space.  I'm really not sure how prevalent this is with CHD's though.

Merged  = Borrows multiple files from other titles  (least amount of storage space required)

Split = Less so

Non-Merged = No dependency on other titles   (most amount of storage space required)

Say NFL blitz shares a common file with NBA Jam that is located in the NBA Jam folder (which you throw out).  In a merged set scenario, NFL Blitz becomes non-working.

This is hypothetical only.

 

So this makes things difficult.  I can find out the file name of a Rom file for a game by running MAME and bringing up the mini-GUI.  If the CHD files doesn't go by the same name then I am out of luck figuring out the relationships as I don't think the necessary CHD's for a game are listed anywhere separately.

[tthurman]

I'm not explaining this very well, it's not the name but the files within the folders.  Again I'm not sure how much it pertains to CHDS, but they are merged in every instance I've seen.

 

Quoted from:  Demystifying MAME

 

Quote

So which is best? Non-Merged/Split or Merged

There is no easy answer to that, it will depend on your circumstances and what you intend to do with the ROMS when you have them.

• If disk space is an issue you can save 20GB using a Merged set instead of a Split set but your frontend (if you use one) may not be able to tell that you have a game available if it is a clone.
• If you want to be able to delete the ROMS you don’t want without breaking others, you need a Non-Merged set but it will take up a huge amount of space until you are done deleting.
• If you want something between the two extremes above, a Split set is for you but deleting a Parent set, a BIOS set or a Device will kill all the other ROM sets dependent upon it.