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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.
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
URL: http://www.cs.ncl.ac.uk/publications/trs/papers/30.pdf
