Browse Prior Art Database

Virtual Memory 370 Simulator

IP.com Disclosure Number: IPCOM000084752D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Winters, RM: AUTHOR

Abstract

There is no method of estimating the performance of an application or operating system under VM/370 without actually running under the VM/370 Supervisor. The VM/370 Simulator allows this by simulating the VM/370 Supervisor. Performance monitors can be used with the VM/370 Simulator to obtain timing statistics that should help in the migration of application or operating systems to VM/370.

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Virtual Memory 370 Simulator

There is no method of estimating the performance of an application or operating system under VM/370 without actually running under the VM/370 Supervisor. The VM/370 Simulator allows this by simulating the VM/370 Supervisor. Performance monitors can be used with the VM/370 Simulator to obtain timing statistics that should help in the migration of application or operating systems to VM/370.

The VM/370 Simulator is patterned after the VM/370 Supervisor. The VM/370 Supervisor operates as a "hypervisor" and all operating systems running on VM/370 execute in the problem state. Every attempt to issue a privileged instruction causes a privileged program check interrupt to occur. The interrupt is intercepted by the VM/370 Supervisor which performs the function of the privileged instruction and returns control to the interrupted program.

The VM/370 Simulator also acts as a hypervisor. It overlays the program check NPSW with the entry point of the Simulator. It turns on the problem state bit in each of the other NPSWs. Thus when the VM/370 Simulator is active, the operating system and the application programs execute in the problem state in much the same manner as if they were executing under VM/370.

The VM/370 Supervisor also simulates input/output (I/O) configurations for each operating system and allows multiple operating systems to execute simultaneously. The VM/370 Simulator could be designed to simulate some of this; however, to keep it si...