We needed more accurate control of the 'stepper motor' that moves the read/write 'head' than we had previously.Īlso most of these disks additionally checked the computer's ROM (to prevent them from running on clones, for what reason we're not entirely sure) and so they only worked on an Apple II+.

While it's awesome the WOZ file format was able to reproduce the spiral pattern created by the SpiraDisc system accurately, it meant our emulation of the Apple's Disk II floppy drive system needed a bit of refinement. Every quarter-rotation of the disk the head was moved a quarter of a track! This made it impossible for disk-copying software available at the time to duplicate them. SpiraDisc was a complicated copy-protection system used with some Apple II games such as Frogger and Jawbreaker to prevent piracy.

Once again, Apple II super-cracker 4am has provided us with a challenge.