microM8 Update: Apple II+ emulation and SpiraDisc support

Swirling adventures in copy protection

Pest Patrol disk ‘image’ created with John Morris’ Applesauce disk archiving system

Once again, Apple II super-cracker 4am has provided us with a challenge. SpiraDisc was a complicated copy-protection system used with some Apple II games such as Frogger and Jawbreaker to prevent piracy. 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. 


Lunar Leeper disk ‘image’ created with Applesauce

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. We needed more accurate control of the ‘stepper motor’ that moves the read/write ‘head’ than we had previously.  

Also 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+. We initially didn’t see any reason for microM8 to emulate anything other than an enhanced Apple IIe but now there is, and so since we had added profiles for CP/M support we added a profile for the Apple II+ and the unenhanced Apple IIe. 

If you want to try out these ‘spiradiscs’ yourself, you can find them in the microM8 file catalog in /appleii/disk images/woz/spiradisc/ – just remember to change the ‘profile’ to Apple II+ using the ‘burger’ menu as shown in the example below:

If you already have a copy of microM8, it should self-update on opening, otherwise you can download it from:


There are builds of microM8 for Windows, macOS / OSX and Windows. And it’s free!

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