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Is Supervisor - State Necessary

Lookup NU author(s): Dr Charles Snow



The role of the ""Supervisor-state, Problem-state"" dichotomy in machine architecture is examined. These two states are implemented in machines to facilitate the protection of vital information contained in hardware registers or memory which, if improperly changed, would affect the correct operation of the system. The same kind of protection can be achieved with address mapping techniques resembling those found in existing hardware. Thus the supervisor-state and the privileged operations defined by it can be eliminated, and all programs at all levels of the system can be run on machines with an identical hardware order code. In particular, a copy of an operating system may be run as a job under itself. An example is presented of the design of a machine with a base-limit form of address relocation and no supervisor state. It is conjectured that similar techniques could be applied to machines with more sophisticated structures.

Publication metadata

Author(s): Snow CR, Lauer HC

Publication type: Report

Publication status: Published

Series Title: Computing Laboratory Technical Report Series

Year: 1971

Pages: 14

Print publication date: 01/12/1971

Source Publication Date: December 1971

Report Number: 30

Institution: Computing Laboratory, University of Newcastle upon Tyne

Place Published: Newcastle upon Tyne