Īlthough Spectre GCR would run in 1MB of memory, 2MB or more was recommended. The Spectre GCR plugged into the cartridge slot, and modified the frequency of the data to/from the single-speed floppy drive of the Atari ST, thus allowing it to read Macintosh GCR format discs which required a multi-speed floppy drive. The emulator runs best with a high-resolution monochrome monitor, such as Atari's own SM124, but will run on colour displays by either displaying a user-selectable half of the Macintosh screen, or missing out alternate lines to fit the lower resolution colour display. This avoided any legal issues of copying Apple's software. The Spectre GCR required the owner to purchase a set of official Apple Macintosh 128K ROMs and the Macintosh Operating System 6.0.8 disks. It was the final Macintosh emulator for the ST, and replaced the previous products Magic Sac and Spectre 128. Designed by David Small and sold through his company Gadgets by Small, it essentially turned the Atari ST into an Apple Macintosh computer.
The Spectre GCR was a hardware add-on to the Atari ST computers that plugged into the cartridge port.
