Roland N. Ibbett

Grand Challenges in Computing: Education---A Summary

The conference on grand challenges, held in Newcastle on 30 and 31 March 2004, occurred at a particularly opportune time. The strand on the educational aspects was particularly relevant and the idea innovative in the sense that this was the first occasion on which a grand challenge event with a focus on educational issues in computing had taken place. This paper provides some of the background and includes a distillation of the educational challenges that emerged from that event.

Real-time multiplexing of dispersed spectra in any wavelength region.

A multiplex technique is described that is binary in nature and that can be used in the observation of a dispersed spectrum in any wavelength region for which a detector exists. The subsequent data processing involves the minimum possible number of operations and can easily be carried out in real time. The number of observations that must be made is also a minimum, equal to the number of spectral elements. Methods of generating the coding and decoding patterns, derived from the simple mathematical formulation of the multiplexing technique, are described.

The MU5 computer system

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Technical note: a hierarchical computer architecture design and simulation environment

A hierarchical computer architecture design and simulation environment (HASE) has been developed at the University of Edinburgh. HASE allows rapid development and exploration of computer architectures at multiple levels of abstraction, encompassing both hardware and software. It has five modes of operation (Design, Model Validation, Build Simulation, Simulate System, and Experiment) which formalize the design cycle and allow a proper separation of concerns among the different phases of simulation activity. The software of HASE itself includes a project data storage facility, a discrete-event simulation engine, graphical display/ editing mechanisms, a visualization mechanism, and tools for setting up experiments and gathering results. HASE has been used in a number of research and student projects and these exemplify many of the interesting features of HASE and their relation to designing, simulating and evaluating scalable systems. They include the modeling of scalable implementations of the hierarchical PRAM model of parallel computation on a 2-D mesh, the evaluation of the performance of multiprocessor interconnection networks, and a model of the Stanford DASH architecture.

The development of the MU5 computer system

Following a brief outline of the background of the MU5 project, the aims and ideas for MU5 are discussed. A description is then given of the instruction set, which includes a number of features conducive to the production of efficient compiled code from high-level language source programs. The design of the processor is then traced from the initial ideas for an associatively addressed “name store” to the final multistage pipeline structure involving a prediction mechanism for instruction prefetching and a function queue for array element accessing. An overall view of the complete MU5 complex is presented together with a brief indication of its performance.

The MU5 Instruction Pipeline

MU5 is a high speed general purpose computer designed to meet the requirements of high level languages. The order code is such that several distinct operations are involved in accessing an operand. Operands specified directly by instructions are accessed by the instruction processing unit described in this paper. This unit is designed as a pipeline in which several instructions are in different stages of processing at any one time. A significant improvement in performance is obtained by this technique although detailed requirements of the order code deteriorate the performance in practice. An assessment of the expected overall performance is given.

HASE DLX simulation model

This DLX architecture model offers a variety of visualization mechanisms. Instructors use HASE both as a demonstration tool and as a platform for programming exercises through which students learn to appreciate the importance of code optimization at the software-hardware interface.

HASE: A Flexible Toolset for Computer Architects

HASE is a Hierarchical computer Architecture design and Simulation Environment (HASE) which allows for the rapid development and exploration of computer architectures at multiple levels of abstraction, encompassing both hardware and software. The components of a computer system lend themselves naturally to being modelled as objects, so HASE has been implemented in an object- oriented language. Within HASE there are graphical entity design and edit facilities, entity library creation and retrieval mechanisms, an animator, and statistical analysis and experimentation tools for deriving system performance metrics. HASE uses an object-oriented database management system (ObjectStore) to make the design objects and the entity library persistent. For each architecture model HASE allows many experiments with varying parameters to be performed. The database facilities provided through HASE manage not only the results of each experiment, but also their relationship to the state of the architecture model that produced these results, including all input and output parameters and their values during the experiment. This paper describes the design of HASE, some of the varied projects which have used it, and the future direction of the system.

Context flow: An alternative to conventional pipelined architectures

In an earlier paper [Topham, Omondi, and Ibbet 1988] we reviewed conventional approaches to the design of conventional pipelined architectures and concluded that the underlying limitations of these techniques necessitate radical alternatives. This paper discusses one such alternative,micromultiprogramming, and examines several implementation proposals based on this approach. The weaknesses of these proposals are highlighted, and it is argued that they can be eliminated within the unifying theory of context flow architectures. Implementations of uniprocessor and multiprocessor context flow architectures are considered.

Hierarchical Architecture Design and Simulation Environment

The Hierarchical Architecture Design and Simulation Environment (HASE) is a tool for modelling and simulating computer architectures. Using HASE, designers can create and explore architectural designs at different levels of abstraction through a graphical interface based on X-Windows/Motif and can view the results of the simulation through animation of the design drawings.<<ETX>>