Wang Laboratories, Inc.

Patrick Klos

David J Angel

James P Moskun

Loren O Albright

Carol W Tyler

Emulation method and apparatus allowing a first system, which is not designed as a functional duplicate of a second system, to emulate the second system. The input/output structure of the second system is emulated in the first system by means of routines stored therein and which direct the already existing input/output structure to operate in the same manner as the input/output structure of the second system. The emulation routines are in turn invoked through the non-maskable interrupt mechanism of the first system by a modification thereto which detects the occurrence of 'foreign' input/output requests; that is, input/output requests occuring in programs originally written for the second system and which are not normally recognized by the first system. The means for detecting foreign input/output requests includes means for comparing input/output request port addresses to the range of port addresses occupied by the system input/output devices and indicating when a port address is within the range of address space occupied by the system input/output devices. The foreign request detection means generates a non-maskable interrupt to invoke an input/output emulation routine upon the occurrence of input/output requests which do not normally fall within the range of input/output ports supported by the first system.

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Nashua, NH, United States of America

Patrick Klos