Abstract: An emulating data processor includes a host system and an emulating processor with outputs to and inputs from the host system. The emulating processor executes sequences of instructions executable by a PC being emulated, but a host processor independently executes sequences of its instructions which are different from PC instructions. Circuitry monitors the emulating processor outputs and provides information to the host system so that it can emulate the environment of the PC CPU, emulating both memory and I/O devices. The memory accesses of the emulating processor are mapped into the host system memory, so that the host processor is protected from defective PC software on the emulating processor. The display updates of the emulating processor are detected and provide information for the host processor in updating a part of its display which provides the information a PC display would provide simultaneously with the display characteristic of the host system.

Abstract: An emulating data processor includes a host system and an emulating processor with outputs to and inputs from the host system. The emulating processor executes sequences of instructions executable by a PC being emulated, but a host processor independently executes sequences of its instructions which are different from PC instructions. Circuitry monitors the emulating processor outputs and provides information to the host system so that it can emulate the environment of the PC CPU, emulating both memory and I/O devices. The memory accesses of the emulating processor are mapped into the host system memory, so that the host processor is protected from defective PC software on the emulating processor. The display updates of the emulating processor are detected and provide information for the host processor in updating a part of its display which provides the information a PC display would provide simultaneously with the display characteristic of the host system.

Abstract: Mouse emulation includes two modes, a host mode in which the pointer behaves as the pointer of the host system and an emulating mode in which the pointer behaves as the pointer of the target system being emulated. The display of the target system appears in an emulation window within the host system display. The user can switch from host mode to emulating mode by clicking a mouse key when the pointer is located in the emulation window which also serves to make the emulation window the input focus for receiving user input signals from the keyboard. The user can switch from emulating mode to host mode by depressing a STOP key, a keystroke which need not be provided to the emulator because it would not be provided to the target system's CPU. Mouse related data is transferred to the emulator through a data structure in a reserved memory space which a mouse application does not access, such as the BIOS area if an IBM PC is being emulated.