ROM cartridge
Many CP/M machines were designed to allow the full 16-bit address space of 64 kB to be populated by memory. This was problematic on the Exidy Sorcerer. 32 kB could easily be populated. Another 16 kB was the ROM cartridge address space. This could be populated, but required disabling the ROM cartridge capability. The last 16 kB was required by the system for I/O, particularly for the video, and would have required extensive system modification.