Xerox Corporation

Abdo G Kadifa

Clayton W Mock

John Bradly Dillon

William C Lynch

Geoffrey O Thompson

Jonathan J Gibbons

Donald R Woods

Perry A Caro

Michael L Tallan

Charles R Fay

Joseph H Binkley

Everett T Neely

Gaya Vukkadala

Jeffery W Lee

John D Wick

Hilary N Hooks

Ronald D Hansen

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. An input/output processor handles I/O operation requests of the emulating processor, using the host system I/O devices to emulate some of the PC I/O devices. Output operations to the printer may go either to a local printer or to a file for subsequent printing, so a buffer which can be unloaded to either destination emulates the PC printer. Floppy operations may be handled either by a floppy disk controller like that of the PC or by a software controller of a file in host rigid disk memory which may be accessed as a PC floppy disk, so that a data structure containing parameters of the operation is loaded and provided to the appropriate controller. Rigid disk operations are handled by another file in host rigid disk memory which may be accessed as a PC rigid disk, and an appropriate I/O operating system routine is provided so that the emulating processor can pass the operation parameters through to the host rigid disk controller in a group of registers. Keyboard input operations may come either from the host keyboard or directly from a data structure managed by the host processor, in each case converted to PC codes, and another buffer which can be loaded from either source emulates the PC keyboard. The host system emulates the environment of the emulating processor while emulating the user interface of the PC.

Data processing system emulation in a window with a coprocessor and I/O

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. An input/output processor handles I/O operation requests of the emulating processor, using the host system I/O devices to emulate some of the PC I/O devices. The host system emulates the environment of the emulating processor while emulating the user interface of the PC.

Emulation with display update trapping

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. A mouse driver which provides standard responses to service requests from the application retrieves this data from the data structure, making hardware ports or software emulating or bypassing such ports unnecessary.

Mouse pointer with switchable emulation mode

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Palo Alto, CA, United States of America

Abdo G Kadifa