Unisys Corporation

Dave Q Anderson

Michael J Rieschl

Kurt N Johnson

Qingyan Chen

A main memory simulation system includes storage files, a cache buffer, and an interface. The storage files includes both a fast look-up table and a slow look-up table. The fast look-up table is operable to directly obtain a page address that has been allocated to a main memory address while the slow look-up table is operable to first determine if a page address has been allocated to a main memory address and then to obtain the allocated page address. The interface operates to receive a request for transfer of main memory, in the form of a main memory address, from a storage file to the buffer of the cache. The interface responds by performing a page transfer between the storage file and buffer according to the page address that has been allocated to the requested main memory address, as found in the fast or slow look-up table.

Apparatus and method for the simulation of a large main memory address space given limited resources

Emulation of a hardware peripheral is accomplished through use of object oriented software and runs in an object oriented environment. Particular adaptation of an emulation to enable specific data storage magnetic tape drive peripheral is described. Use of emulators in general enables continued reliance on legacy hardware and software without maintaining an entire suite of legacy hardware. Simplified emulation structure enabled by object oriented programming described herein makes migration from legacy systems feasible in stages at relatively low cost. In set-up and in use, users can have control over instances of emulator objects, including association with data files that operate as virtual storage media whether initially associated with the emulator or not, using a simple window-based interface for choosing particular data files, opening them, opening new instances of emulator objects and so forth. Variations are also described. Legacy programming is handled by use of legacy instructions communicated to the emulated object instances, which the object instances respond to appropriately.

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Coon Rapids, MN, United States of America

Dave Q Anderson