A discussion is presented as to how simulation can be used as an effective management tool to reduce costs by predicting many software requirements and design problems that are inherent in the development of real-time...
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A discussion is presented as to how simulation can be used as an effective management tool to reduce costs by predicting many software requirements and design problems that are inherent in the development of real-time computer programs. Historically, simulation has been applied primarily to system performance evaluation and logic verification, and only recently has been formally used to help control the development of the operational program in a U. S. Navy tracking system. Since the technique is still under evaluation, the paper discusses the general concepts.
This article describes an operating system for use in a reconfigurable redundant computer system employing a synchronized multicomputer organization. The ″synchronous″ executive used in conjunction with a multicompu...
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This article describes an operating system for use in a reconfigurable redundant computer system employing a synchronized multicomputer organization. The ″synchronous″ executive used in conjunction with a multicomputer provides for a fault-tolerant computer system in which the software operation is insensitive to the level of redundancy, computer malfunctions, and individual computer re-initializations. This system supported by the synchronous executive provides for independence of the application and executive software from redundancy management.
A network version of the SPEAKEASY system is described that consists of a series of dynamically linked modules that perform the necessary language and system protocols. These protocols are transparent to the user, pro...
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A network version of the SPEAKEASY system is described that consists of a series of dynamically linked modules that perform the necessary language and system protocols. These protocols are transparent to the user, producing a language that has additional power without additional complexity. The language uses attached libraries to provide the necessary information that will tailor the system to a specific network, and to supply on-line documentation. Since the modules are compiled code, the generality of the system does not produce a large overhead.
The paper presents a method for predicting the paging rate of a virtual memory multiprogramming system, given the set of programs to be run together, and the size of available main storage. Predictions compare favorab...
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The paper presents a method for predicting the paging rate of a virtual memory multiprogramming system, given the set of programs to be run together, and the size of available main storage. Predictions compare favorably with results from a CP-67 simulation.
The Dartmouth Time Sharing System (DTSS) had a mean time between failures of 41 hours for the 1972 calendar year. During this period, the system was available for 6047 hours, and over 4. 3 million jobs were run for 13...
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The Dartmouth Time Sharing System (DTSS) had a mean time between failures of 41 hours for the 1972 calendar year. During this period, the system was available for 6047 hours, and over 4. 3 million jobs were run for 13,000 users at 50 colleges and high schools in the U. S. and Canada. The purpose of this paper is to describe some of the techniques used to achieve a high degree of service reliability in a system undergoing continual development and improvement. The first part of the paper provides a brief description of DTSS and defines the concepts of ″jobs″ and ″failures″ as used in this environment. Subsequent parts of the paper describe the software techniques and management strategy used to achieve system reliability objectives.
The purpose of this paper is to consider the problem of validation as it applies to the development of discrete digital simulation models. The described validation techniques, discussed in the context of model develop...
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The purpose of this paper is to consider the problem of validation as it applies to the development of discrete digital simulation models. The described validation techniques, discussed in the context of model development, are utilized during the developmentf of a simulation model of the Univac 1108 Exec 8 computer system at the Marshall Space Flight Center in Huntsville, Alabama. These techniques are of a general nature and are demonstrated with examples from the Univac 1108 Exec 8 simulation model development.
This article develops the theory of the statistical dynamics of a fixed degree of multiprogramming Markov process model. The model is a generalization of Buzen's central server model and permits the inclusion of s...
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This article develops the theory of the statistical dynamics of a fixed degree of multiprogramming Markov process model. The model is a generalization of Buzen's central server model and permits the inclusion of such features as multiple central processing units and direct access storage devices with rotational position sensing and sector queueing.
This article is written from the point of view of the design of today's large and complex real-time computer-based control systems using multi-processor computers. The article may be viewed in terms of three level...
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This article is written from the point of view of the design of today's large and complex real-time computer-based control systems using multi-processor computers. The article may be viewed in terms of three levels of definition of software reliability: a) an overall or high-level definition, b) an intermediate-level definition (which might be termed a system designer's definition), and c) a low-level, measurement, or nitty-gritty definition. In these terms, the high-level definition of software reliability is clear. A comparison of software with hardware is used to develop ″system manager's″ definitions of both hardware and software reliability, which differ for stated reasons. The low-level definition is probed, and two definitions are offered; the one that is philosophically satisfying seems to be impracticable and vice versa. Some remarks are included on the particular difficulty associated with a control system that is used continuously on the traffic for which it was designed - e. g. , an air-line, in-flight traffic-control system or a telephone switching system.
Investigation of the application of minimal-total-processing-time (MTPT) scheduling disciplines to rotating storage units when random arrival of requests is allowed. Fixed-head drum and moving-head disk storage units ...
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Investigation of the application of minimal-total-processing-time (MTPT) scheduling disciplines to rotating storage units when random arrival of requests is allowed. Fixed-head drum and moving-head disk storage units are considered and particular emphasis is placed on the relative merits of the MTPT scheduling discipline with respect to the shortest-latency-time-first (SLTF) scheduling discipline. The results of the simulation studies presented show that neither scheduling discipline is unconditionally superior to the other. For most fixed-head drum applications the SLTF discipline is preferable to MTPT, but for intra-cylinder disk scheduling the MTPT discipline offers a distinct advantage over the SLTF discipline. An implementation of the MTPT scheduling discipline is discussed and the computational requirements of the algorithm are shown to be comparable to SLTF algorithms. In both cases, the sorting procedure is the most time consuming phase of the algorithm.
This article describes a simulator for Register Transfer Modules (RTM's). The simulator operates at the register transfer level. RTM systems are specified to the simulator with a language which was designed to all...
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This article describes a simulator for Register Transfer Modules (RTM's). The simulator operates at the register transfer level. RTM systems are specified to the simulator with a language which was designed to allow simple translation from an RTM flow chart.
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