James Leslie Keedy

Support for Objects in the MONADS Architecture

The paper outlines those features of the MONADS computer architecture which support object-oriented programming. It begins by describing the MONADS view of objects and then shows how objects are efficiently supported in the system’s large persistent uniform virtual memory. Direct architectural support for objects in stack and heap segments is discussed, and the idea of module capabilities and module call segments as a technique for efficiently invoking the operations of persistent major objects in a protected way is also described. Following a description of the underlying memory structure and its use of capability based addressing, the paper concludes with a short discussion of garbage collection, local area networks and a massive memory version of the hardware.

A massive memory supercomputer

An approach to supercomputing that is based on using a massive main memory (in the order of gigabytes) is investigated. Many of the problems currently solved on conventional supercomputers can equally be solved in similar time on such a machine, with a modest processor speed. The advantages of this approach in supporting database applications, VLSI applications and many other applications working on large volumes of date are examined. It is shown how the architecture of the MONADS-PC system, a capability-based computer developed by the authors, can be adapted to support such a large memory. The architectural design of a machine based on MONADS-PC is given, with special emphasis on the addressing and address translation issue.<<ETX>>

Addressing mechanisms for large virtual memories

Traditionally there has been a clear distinction between computational (short-term) memory and filestore (long-term memory). This distinction has been maintained mainly due to limitations of technology. Recently there has been considerable interest in programming languages and systems which support orthogonal persistence. In such systems arbitrary data structures may persist beyond the life of the program which created them and this distinction is blurred. Systems supporting orthogonal persistence require a persistent store in which to maintain the persistent objects. Such a persistent store can be implemented via an extended virtual memory with addresses large enough to address all objects. Superimposing structure and a protection scheme on these addresses may well result in them being sparsely distributed. An additional incentive for supporting large virtual addresses is an interest in exploiting the potential of very large main memories to achieve supercomputer speed. This paper presents hardware and software mechanisms to implement a paged virtual memory which can be efficiently accessed by large addresses. An implementation of these techniques for a capability-based computer, MONADS-PC, is described.

Persistent protected modules and persistent processes as the basis for a more secure operating system

The MONADS computer architecture is based on a very large persistent virtual memory which eliminates the need for a conventional file store and filing system, thus providing a suitable basis for persistent programming. The architecture also provides direct support for persistent objects (modules), which are protected by capabilities, and for processes which persist not only between login sessions but also over system shutdowns. The authors briefly outline these aspects of the architecture and describe how they are used in the design of the MONADS operating system. They then show how these features naturally give rise to a wide range of security advantages which would be very difficult to achieve in conventional systems. They first discuss the security advantages of persistent protected modules and then they consider how persistent processes are organised, how they relate to modules and how they contribute to stronger security. Next they describe how users can communicate despite the protection mechanisms and how such communication can be carried out securely. Then follows a concluding discussion of the security and other advantages of a persistent architecture and an indication of the direction of future work.<<ETX>>

Uniform support for collections of objects in a persistent environment

The LEIBNIZ programming language, developed as part of the MONADS project at the University of Newcastle, NSW, supports implementation-independent high-level constructs, based on sets and sequences, for manipulating collections of objects in such a way that the compiler can be guided to select a suitably efficient implementation mechanism. The authors describe the relevant LEIBNIZ constructs and discuss how the structure of the compiler allows novel implementations, written in LEIBNIZ, to be added. At present a Pascal compiler exists for the MONADS-PC and a LEIBNIZ compiler (translating into Pascal) is currently under development. The authors have formulated the rules necessary to produce the transformations from LEIBNIZ to Pascal, using implementation modules, and these have recently been incorporated into the compiler. The resulting Pascal code was then tested and found to be correct.<<ETX>>

A Capability-Based Massive Memory Computer

Conventional supercomputers gain their speed from the use of complicated and expensive multi-stage processor designs and/or the employment of a large number of simple processors working in parallel. This paper investigates another approach, based on using a massive main memory (in the order of gigabytes). The paper discusses the advantages of this approach in supporting database applications, VLSI applications and many other applications working on large volumes of data. It is shown how the architecture of the MONADS-PC system, a capability-based computer developed in Australia by the authors, can be adapted to support such a large memory. The architectural design of a new machine based on MONADS-PC is given, with special emphasis on the addressing and address translation issue.

A model for security and protection in persistent systems

Abstract The architectural model for the support of orthogonal persistence proposed in this paper is based on persistent modules (both for code and files) uniformly structured according to the information-hiding principle, persistent processes based on the procedure calling model, and persistent module capabilities. It is shown how this combination of features can provide a strong basis for very secure operating systems in terms of user authentication, file security, directory security and communication between users. An implementation based on the MONADS-PC computer is briefly described.

Security in a Persistent Distributed Operating System

The MONADS computer architecture is based on a very large persistent virtual memory which eliminates the need for a conventional file store and filing system. This architecture supports persistent objects (modules) which are protected by capabilities and processes which persist not only between login sessions but also over system shutdowns. These features naturally give rise to a wide range of security advantages which would be very difficult to achieve in conventional systems. In this paper we describe these security advantages and discuss how they can easily be carried over to a distributed environment.