SUDDEN DESU

The Atari File Management Subsystem (FMS) is the filesystem on an Atari 810 floppy disk.

The 720 sectors of the disk were numbered from 1 to 720, but (perhaps due to poor communication between the different development teams at Atari) the FMS filesystem was designed to support sector addresses in the range from 0 to 719, which meant that sector 720 was not addressable but a nonexistent sector 0 was. This resulted in the filesystem only using the 719 sectors in the overlap between what is addressable and what actually exists, so sector 720 is unused (a waste of a perfectly good 128 bytes).

I noticed this menu a while back in Magical Error wo Sagase, a puzzle game where you search for differences between two images. In the past I was able to load the routine, but I guess the stack wasn’t set up properly, and it would reset the game immediately after the text appeared. I took a second look at the disassembly tonight and had much better success.

I was pretty unhappy that Land Maker, one of my favorite arcade puzzle games, was one of the few Taito F3 games that did not have the Taito code implemented. Despite that, I still had a hunch there may be some leftovers worth investigating. And I was right! I wouldn’t be making a post otherwise…