Kelv's Random Collection

A random collection of my contributions to the world.

SimCity 2000 Saved Cities

Posted by kelvSYC on 7-20-2014

Here’s a break from the constant madness that is ROM hacking: the SimCity 2000 Saved Game file format.

SimCity 2000 largely follows the Interchange File Format standard, with the notable exception of the requirement that chunks be aligned on two-byte boundaries.  Other notes:

  • Most of the data within the SimCity 2000 save file is compressed using a form of run-length encoding.  The RLE structures are mapped out, but I’ve not really implemented the script elements that will map them.  This is because scripting is buggy and is a huge performance hit on the build (it’s a prerelease build that fixes a few bugs from the last official build, as explained in an earlier post).  I’ve been told that the next release will fix this issue, but I don’t have even that build yet.
  • Synalyze It! can’t really parse decompressed data while the data is compressed.  The true meat-and-potatoes of the SimCity 2000 data is in fact compressed.
  • CNAM chunks may occur at the end of a file, but I have not seen any save that has that.
  • The string in the CNAM chunk appears to be “dirty Pascal string”.  Perhaps putting it as a C-string starting at the second byte might be better.

Hopefully I can get a generic IFF grammar going, as well as its cousin the RIFF, based on this.

Changelists after the break.

Download the SimCity 2000 Saved City Grammar here!

Changes for 7-21-14:

  • Initial release.  Almost everything that’s not compressed has been mapped out.

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