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A POSTMORTEM FOR A TIME SHARING SYSTEM

HOWARD EWING STURGIS

CSL 74-1 JANUARY, 1974

Abstract:

This thesis describes a time sharing system constructed by a project at the University of California, Berkeley Campus, Computer Center. The project was of modest size, consuming about 30 man years. The resulting system was used by a number of programmers. The system was designed for a commercially available computer, the Control Data 6400 with extended core store. The system design was based on several fundamental ideas, including: The abstract machine defined by the first implementation layer provided 8 types of abstractly defined objects and about 100 actions to manipulate them. Subsequent layers provided a few very complicated additional types. Many of the fundamental ideas served us well, particularly the concept that the system defines an abstract machine, and capability based protection. However, the attempt to provide a mapped address space using unsuitable hardware was a disaster. This thesis includes software and hardware proposals to increase the efficiency of representing an abstract machine and providing capability based protection. Also included is a description of a crash recovery consistency problem for files which reside in several levels of storage, together with a solution that we used.
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Paul McJones
1998-06-22