Comment by nxobject

One way to add devices that doesn't require ROM or software modification, but _does_ require modifying the emulator: create a virtual memory-mapped device off 68K bus, and write a driver/CDEV to drive it. The SE and Macintosh II had blessed but different expansion options, after all.

For earlier models, there are unused apertures in model memory maps that are at least 2KB large, but they do differ between models.