Time-shared Cathode Ray Tube

Time-shared cathode tube provides high quality display at low cost display stations which utilize television moniters. It updates a cluster of graphic displays from a computer and is useful in systems not equipped for graphics time-sharing

MZnet : mail service for personal micro-computer systems

Traditional computer mail systems involve a co-resident User Agent (UA) and Mail Transfer System (MTS) on a time-shared host computer which may be connected to other hosts ina network, with new mail posted or delivered directly through co-resident mail-slot programs. To introduce personal micro-computers (PCs) into this environment requires modification of the traditional mail system architecture. To this end, the MZnet project uses a split-slot model, placing UA programs on the PCs while leaving MTA programs on a mail relay host which can provide authentication and buffering. The split-slot arrangement might be viewed as a new protocol level which operates somewhere between the currently defined MTS-MTS and UA-UA levels

Marshall system for aerospace system simulation (MARSYAS), user's manual

The capabilities of the Marshall system for aerospace system simulation (MARSYAS) and how to use it are described. MARSYAS is a software system that allows easy setup and control of the simulation of the dynamics of large physical systems on a digital computer. The physical systems are modeled in the form of block diagrams or equations. The blocks can have multiple inputs and multiple outputs, and they can be nested to form hierarchies. The block diagrams can contain transfer functions, nonlinear and logical functions, equations, analog computer elements and FORTRAN programs. The input format of the equations can be combinations of nonlinear, time-varying differential equations and algebraic equations in their original format. MARSYAS could also serve as a storage and retrieval system for models as a basis for a model configuration control system on a central time-shared computer. The outputs of the simulation system can be not only time-responses but also other analysis data such as frequency response, power spectrum and stability parameters. The MARSYAS translator is written in FORTRAN running on the Univac 1108 computer under the EXEC 8 operating system

Optimization techniques for time-shared computer systems

The inefficiency of time-shared computer systems compared to batch processing systems is in the time lost in swapping operations. The larger the allocated quantum size, the less swap time is incurred. In order to guard against intolerable response time while lengthening the quantum size, the response time of a common request must be regulated. The criteria used in this paper to regulate the response time is to vary the quantum, with the number of users in the system, in such a way that the computer response time approaches the human response time. Based upon this concept, models are designed and analyzed to design an optimal scheduling algorithm which allocates the quantum dynamically. The models proposed are based upon Markovian assumptions for both arrival and service times. The priority discipline is round robin with dynamic quantum allocation. The swap time is assumed to be constant and the overhead time is zero. The inverse measure of performance is assumed to be the expected square difference between the cycle time and the mean human response time. In order to optimize these models two techniques are discussed. In the first, a mathematical optimization model is formulated in which a Markov chain is imbedded at the epochs of the beginning of a cycle. The cost function is assumed to be the inverse measure of performance. A technique suggested by Howard for optimizing a stochastic system under Markovian assumptions provides an optimal policy by which the scheduling algorithm allocates the quantum. The second technique discussed is based upon an optimal control system approach. The quantum size is chosen in such a way as to assure some stability property while improving system performance. A numerical example which illustrates these methods is provided

Voter comparator switch provides fail safe data communications system - A concept

System indicates status of computers and controls operational modes. Two matrices are used - one relating to permissible system states, the other relating to requested system states. Concept is useful to designers of digital data transmission systems and time shared computer systems

Investigations of collaborative design environments: A framework for real-time collaborative 3D CAD

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This research investigates computer-based collaborative design environments, in particular issues of real-time collaborative 3D CAD. The thesis first presents a broad perspective of collaborative design environments with a preliminary case study of team design activities in a conventional and a computer mediated setting. This study identifies the impact and the feasibility of computer support for collaborative design and suggests four kinds of essential technologies for a successful collaborative design environment: information-sharing systems, synchronous and asynchronous co- working tools, project management systems, and communication systems. A new conceptual framework for a real-time collaborative 3D design tool, Shared Stage, is proposed based upon the preliminary study. The Shared Stage is defined as a shared 3D design workspace aiming to smoothly incorporate shared 3D workspaces into existing individual 3D workspaces. The addition of a Shared Stage allows collaborating designers to interact in real-time and to have a dynamic and interactive exchange of intermediate 3D design data. The acceptability of collaborative features is maximised by maintaining consistency of the user interface between 3D CAD systems. The framework is subsequently implemented as a software prototype using a new software development environment, customised by integrating related real-time and 3D graphic software development tools. Two main components of the Shared Stage module in the prototype, the Synchronised Stage View (SSV) and the Data Structure Diagram (DSD), provide essential collaborative features for real-time collaborative 3D CAD. These features include synchronised shared 3D representation, dynamic data exchange and awareness support in 3D workspaces. The software prototype is subsequently evaluated to examine the usefulness and usability. A range of quantitative and qualitative methods is used to evaluate the impact of the Shared Stage. The results, including the analysis of collaborative interactions and user perception, illustrate that the Shared Stage is a feasible and valuable addition for real-time collaborative 3D CAD. This research identifies the issues to be addressed for collaborative design environments and also provides a new framework and development strategy of a novel real-time collaborative 3D CAD system. The framework is successfully demonstrated through prototype implementation and an analytical usability evaluation.Financial support from the Department and from the UK government through the Overseas Research Studentship Awards

On Characterizing the Data Movement Complexity of Computational DAGs for Parallel Execution

Technology trends are making the cost of data movement increasingly dominant, both in terms of energy and time, over the cost of performing arithmetic operations in computer systems. The fundamental ratio of aggregate data movement bandwidth to the total computational power (also referred to the machine balance parameter) in parallel computer systems is decreasing. It is there- fore of considerable importance to characterize the inherent data movement requirements of parallel algorithms, so that the minimal architectural balance parameters required to support it on future systems can be well understood. In this paper, we develop an extension of the well-known red-blue pebble game to develop lower bounds on the data movement complexity for the parallel execution of computational directed acyclic graphs (CDAGs) on parallel systems. We model multi-node multi-core parallel systems, with the total physical memory distributed across the nodes (that are connected through some interconnection network) and in a multi-level shared cache hierarchy for processors within a node. We also develop new techniques for lower bound characterization of non-homogeneous CDAGs. We demonstrate the use of the methodology by analyzing the CDAGs of several numerical algorithms, to develop lower bounds on data movement for their parallel execution