Access Restriction

Author Fabry, R. S.
Source ACM Digital Library
Content type Text
Publisher Association for Computing Machinery (ACM)
File Format PDF
Language English
Subject Keyword Operating systems ♦ Segmentation ♦ Capabilities ♦ Computer utility ♦ Information sharing ♦ Addressing hardware ♦ Protection hardware ♦ Shared addresses ♦ Protection ♦ Addressing ♦ Tagged architecture
Abstract Various addressing schemes making use of segment tables are examined. The inadequacies of these schemes when dealing with shared addresses are explained. These inadequacies are traced to the lack of an efficient absolute address for objects in these systems. The direct use of a capability as an address is shown to overcome these difficulties because it provides the needed absolute address. Implementation of capability-based addressing is discussed. It is predicted that the use of tags to identify capabilities will dominate. A hardware address translation scheme which never requires the modification of the representation of capabilities is suggested. The scheme uses a main memory hash table for obtaining a segment's location in main memory given its unique code. The hash table is avoided for recently accessed segments by means of a set of associative registers. A computer using capability-based addressing may be substantially superior to present systems on the basis of protection, simplicity of programming conventions, and efficient implementation.
Description Affiliation: Univ. of California, Berkeley (Fabry, R. S.)
Age Range 18 to 22 years ♦ above 22 year
Educational Use Research
Education Level UG and PG
Learning Resource Type Article
Publisher Date 2005-08-01
Publisher Place New York
Journal Communications of the ACM (CACM)
Volume Number 17
Issue Number 7
Page Count 10
Starting Page 403
Ending Page 412

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Source: ACM Digital Library