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Operating System

Pegasus has been concerned with the study of how to provide a general purpose multimedia application platform to replace the plethora of special purpose, application specific solutions. Pegasus delievered a operating system Nemesis, which provides a platform on which application programmers can manipulate time-constrained media data as well as performing the usual capture and replay functions. Nemesis' scheduling system provides predictable performance to applications and informs them of any changes to resource allocation. Pegasus built the operating system kernel, some user libraries, a filing system and some networking facilities.

However, further research and experimental work on the existing kernel, operating system services and filing system is required to provide both improved performance and predictability. Such work must also address these issues under different work profiles, much as Windows-NT Workstation and Server systems provide a similar environment, but with different tradeoffs and services for the different roles.

Industry requires that a new operating system concern itself with the migration of existing applications. Therefore, the system needs to provide a familiar environment to ease the migration of applications designers and programmers. To meet this requirement, Pegasus II will provide standard single- and multi-threaded programming environments (conforming to standards wherever possible); the novel work here is to provide such a model on Nemesis' underlying activation-based execution model, and using the shared single virtual address efficiently. Thus existing applications will co-exist with new applications which exploit the activation based model directly.

The multimedia storage service, developed under Pegasus, will be further extended to accommodate tertiary storage so that it can be used for large-volume storage.

Pegasus II will deliver an operating system that is sufficiently complete to enable distribution to other research groups, both academic and industrial.

Simon Crosby
Thu Nov 7 11:56:58 GMT 1996