The author has developed an emulator for early Macintosh computers powered by the Motorola 68000 CPU and focused on the disk drive controller, IWM, originally designed for 5.25″ drives. The post documents how the CPU interfaces with the controller through memory-mapped I/O lines, enabling commands like track movement and spindle motor control. A surprising detail is the method used to control the spindle motor speed through software in the Macintosh 128K and 512K models. The post also delves into the unique disk format specifics, drive speed variations, and the transition to hardware control in later Macintosh models. It discusses the ROM driver ‘Sony’ and provides insights into decoding sector data for file system operations. The attention to detail and technical depth in this documentation will be valuable to developers working on Macintosh emulation.
https://thomasw.dev/post/mac-floppy-emu/