In this blog I hope to spend time dissecting and rebuilding various software artifacts for the 8-bit Atari.

My first entry is The ABC of CPR, an Edunetics title you can find at http://www.atarimania.com/game-atari-400-800-xl-xe-abc-of-cpr-_12807.html. I decided to look at this because I found the same/similar disks in the DGS and Page 6 public domain disk archives, and I was curious if there were any differences. All the images differ from each other in various ways (seen by hex dumping the disks and comparing), but the differences in the Atarimania copies suggest it is damaged:

In particular, it seems that:

• Side A: Sectors 659 and 675 are empty.
• Side B: Sector 96, all the bytes appear to be shifted forward by one.
  

The Page 6 and DGS copies are themselves not consistent, the DGS copies appear to have a couple of bit flips in sectors 193 and 256, and sector 334 is empty. The bytes in question are consistent between the Page 6 and Atarimania copies.

So given this, I've patched the 3 sectors mentioned above from the Page 6 disks to generate a "fixed" version of Atarimania images.