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MAME Compressed Hard-Drive [CHD] Splitting Tutorial
(Based on WinRAR build 3.00 Beta. Please note that all folders used are not a reflection on the location of the CHD files installed on your system.)

Getting WinRAR...

WinRAR is freely available to download from http://www.rarlab.com/ in the downloads section.

The current version available to download is WinRAR 3.30.

Download the latest executable file from the above location and install to your desired location. Once installed, WinRAR will now appear in your context (right-click) menus.

Once Installed...

... open up Windows Explorer and locate the first CHD File - in this instance, Area 51 (filename:area51.chd).

Right-click on the CHD file and select Add to Archive. You will be presented with a window allowing you to specify the archive name and parameters for compression.

The General tab should be the first one to appear in the window. The archive name should be set to area51.zip by default - leave it at the default name.

Ensure that Archive Format is set to RAR (and not 'ZIP'). Notice that the filename has now changed to reflect the new compression type selected [area51.rar].

Compression Method should be left at Store. Seeing as the CHD Files are already in a compressed state, they do not benefit from using other compression ratios.

Next select Split to Volumes, bytes. Set this at 20,971,520 (20MB chunks). This can be altered manually, depending on how many segments you wish to break the file into, but note that creating too many segments means more possibility for CRC errors.

Archiving options can be set to the following:
  • Delete files after archiving
  • - this is useful if you are short on disk space
  • Create Solid Archive
  • - should be unchecked; only useful if you are actually gaining through compression.

Press enter and sit back while WinRAR does the hard work for you. When complete - presuming you have followed the above options - you should have one CHD file, split into several RAR files.


For the file to be uncompressed back to it's normal state, the first archive in the set (ie: area51.part1.rar) should be selected. Merely set to Extract Files and you're away!

What are PAR files?

Now that the WinRAR part is done, a lot of you may have heard of PAR or Parity files. Parity files allow either the retrieval of compressed archive which are corrupt, or completion of missing archives. Note that this will increase the final size of the of the binaries that are cut back to CD.

SmartPAR can be obtained from http://www.disc-chord.com/smartpar.

To use SmartPAR, select File --> New Parity Set (or [CTRL+N]). This will present you with the look dialogue box which you point to the WinRAR'd files, ie: area51.

Select all the files and press enter. You will then be taken to the Create Parity Options. Ensure that all archives have Recoverable selected. SmartPAR will - by default - select how many Parity files should be created. The more Parity files there are, the better the chance of rescuing bad or missing archives (which is nice), at the expense of increasing the archive size.

When ready, press OK and wait until SmartPAR has finished. The parity files are now ready to be included on your CD burn. nb: Don't forget to include SmartPAR on the CDs!


With the advent of faster and faster CDR, CDRWs and DVDrs, there is an ever increasing chance that the recipient of a binary collection may experience problems ranging from but not limited to -
  • Scratched CDs - either through transit problems or clumsy handling
  • Frostbite - CDs travelling by air transit reach temperatures that will allow CDs to bind together, thus affecting the surface layers.
  • Use of poor CD media - especially silvers (susceptible to frostbite).
  • Compatibility Issues - One other problem that exists, and one that is becoming increasingly common is the ability of differing CDrs being able to read CDs burnt on another type or model.
For example: I own a 4x SCSI CDR and also a 32x CDR. CDs burnt on either or drive do not like to be accessed. What gives? Who knows?

Lets just say that technology standards are not quite.. er.. standard. So, what do you do? Reburn the CDs? No, use a utility like ISOBuster, which allows you to access a CD that is normally unreadable.

This is a great utility and could be used by end users who are experiencing problems. This will ensure that Burners are not having to request reburns due to incompatabilities between burns etc. Again peeps, this is for info only.

If there is any interest I can do a small tutorial on how to use it, but to be honest, if you can use Windows Explorer - then you already know how.

Romulous, Feb 2003

If there are any errors or additions that you wish to make, please do so and forward to the webmaster- thanks for reading this drivel