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Analysis of computer system reliability and maintainability
WORLD
ABSTRACTS
ON MICROELECTRONICS
AND
RELIABILITY
205
being in any of the four possible states) of the network is calculated. It is thus seen to be possible, at least in principle, to calculate the reliability of a relay contact network, taking into account the reliability of the coils which activate those contacts.
with an incandescent lamp while the other operates from a light-emitting diode. Interpretation of photo-transistor data sheets is explained and the article describes the connection to an integrated-circuit logic system for the counting of objects breaking a light beam.
*Multiprocessor systems for reliability--a comparative study. J. R. TAYLOR. AERE-R-7102 Atomic
The effect of equipment reliability upon plant system performance. A. R. nAMES. Proceedings, Internepcon 1972, Brighton, 17-19 October (1972), p. 169.
Energy Res. Est., Harwell, U.K. (1972). Examines some of the problems in structuring both the hardware and software of multiprocessor systems to achieve high reliability. It begins with a review of multi-computer systems, and a description of the advantage of multiprocessor systems. It then compares different techniques for interconnection of hardware components of multiprocessor systems. Techniques for structuring software for real time systems are described; and two ways of implementing this software structure in a multi-processor system are compared. As a result of the comparisons, some techniques for implementation of multi-processor systems are recommended.
Transient-testlng vital to airborne systems reliability. L. S. CORNISH. Electron. Engng, September (1972), p. 61. Short duration voltage-transient spikes can exceed steady-state supply values considerably, and are a cause of component failure and equipment malfunction. This is a well-known fact, but voltagetransient tests carried out at BAC's laboratory show that only 29 per cent of equipment tested met the requirements of the test specifications in full.
Reliability prediction of a two-unit standby redundant system with standby failure. R. C. GARG and S. SAWHNm'. Microelectron. ~ Reliab. 11 (1972), p. 263. In this paper, the distribution of the first time to system failure (FTSF) and the mean time to system failure ( M T S F ) of a standby redundant complex system has been evaluated by using the Laplace-Stieltjes transform. It has been assumed that the switching is instantaneous and after repair a unit recovers its function perfectly.
Analysis of computer system reliability and maintainability. R. LONOBOTTOM. Radio Electron. Engnr 42, No. 12, December (1972), p. 537. Equipment failures on computer systems give rise to more interruptions to service and excessive periods of repair time than a user would expect. This paper examines theoretical and actual reliability and repair statistics, showing how the shortcomings are influenced by test techniques, maintenance engineers, application of the system and spares availability. Various reliability and maintainability parameters are derived from established computer systems, further developed for m o d e m equipment and then considered in relation to the latest computers.
Reliable optoelectronic circuit design. J. BLISS. Semiconductors (1972) (Motorola), p. 17. Two photoelectric systems are described in this article as examples of the design procedure for such circuitry. One operates
T h e reliability of electronic equipment is especially important when such equipment is used in the control of large plant or complex systems. Typically, important plant operational aspects are: (a) the availability requirement; (b) the safety requirement. T h e availability requirement usually demands that the plant must operate continously over a specified minimum percentage of the total specified operating time. U n scheduled plant shutdowns due to equipment failures can be very costly and may involve thousands of pounds per hour in lost production. Availabilities in the range of 90-99 per cent are acceptable in many cases. In contrast, the safety requirement usually demands that the plant must shut down should dangerous conditions begin to arise so as to guard against possible damage to costly plant and possible hazards to the public and the operating personnel. In some applications, fail-dangerous probabilities may need to be in the region of 10-4-10 -7 per year or per operation. A n e w reliability prediction method for hybrid circuits. R. R. BRITTON. Proceedings Internepcon 1972, Brighton, 17-19 October (1972), p. 184. The intrinsic reliability of thick-film hybrid integrated circuits is higher than that of equivalent discrete circuits for several reaons: (1) The number of connections between components is reduced to a minimum. Component leads are eliminated so that only the few connections external to the module are subjected to rigorous assembly processes, such as lead forming. (2) Hybrid assembly processes are fewer and are accurately controlled, generally by automatic machines--screen printer, belt furnace, ultrasonic bonder, etc. (3) The small size and rugged construction gives a high degree of protection from shock and vibration stress. (4) The small size allows homogeneous protection of all circuit components from humidity stress by means of hermetic or plastic packaging. T h e high conductivity of the alumina substrate provides a stable, predictable thermal macro-environment. This paper describes work currently being undertaken at the Product Assessment Laboratories of the Plessey Company. The aim of the work is to provide a technique to enable hybrid manufacturers and users to assess the probability of hybrid circuit failures due to component drift under any relevant stress-life combination.
Effects of test capability on system reliability and availability. G. R. COMPTON,R. S. PRINGLE and P. H. MUEGGLER. IEEE Trans. Reliab. R-21, No. 4, November (1972), p. 239. The impact, on system reliability and availability, of periodic testing with imperfect test equipment is analyzed. T h e proportion of the system tested,
ABSTRACTS
ON MICROELECTRONICS
AND
RELIABILITY
205
being in any of the four possible states) of the network is calculated. It is thus seen to be possible, at least in principle, to calculate the reliability of a relay contact network, taking into account the reliability of the coils which activate those contacts.
with an incandescent lamp while the other operates from a light-emitting diode. Interpretation of photo-transistor data sheets is explained and the article describes the connection to an integrated-circuit logic system for the counting of objects breaking a light beam.
*Multiprocessor systems for reliability--a comparative study. J. R. TAYLOR. AERE-R-7102 Atomic
The effect of equipment reliability upon plant system performance. A. R. nAMES. Proceedings, Internepcon 1972, Brighton, 17-19 October (1972), p. 169.
Energy Res. Est., Harwell, U.K. (1972). Examines some of the problems in structuring both the hardware and software of multiprocessor systems to achieve high reliability. It begins with a review of multi-computer systems, and a description of the advantage of multiprocessor systems. It then compares different techniques for interconnection of hardware components of multiprocessor systems. Techniques for structuring software for real time systems are described; and two ways of implementing this software structure in a multi-processor system are compared. As a result of the comparisons, some techniques for implementation of multi-processor systems are recommended.
Transient-testlng vital to airborne systems reliability. L. S. CORNISH. Electron. Engng, September (1972), p. 61. Short duration voltage-transient spikes can exceed steady-state supply values considerably, and are a cause of component failure and equipment malfunction. This is a well-known fact, but voltagetransient tests carried out at BAC's laboratory show that only 29 per cent of equipment tested met the requirements of the test specifications in full.
Reliability prediction of a two-unit standby redundant system with standby failure. R. C. GARG and S. SAWHNm'. Microelectron. ~ Reliab. 11 (1972), p. 263. In this paper, the distribution of the first time to system failure (FTSF) and the mean time to system failure ( M T S F ) of a standby redundant complex system has been evaluated by using the Laplace-Stieltjes transform. It has been assumed that the switching is instantaneous and after repair a unit recovers its function perfectly.
Analysis of computer system reliability and maintainability. R. LONOBOTTOM. Radio Electron. Engnr 42, No. 12, December (1972), p. 537. Equipment failures on computer systems give rise to more interruptions to service and excessive periods of repair time than a user would expect. This paper examines theoretical and actual reliability and repair statistics, showing how the shortcomings are influenced by test techniques, maintenance engineers, application of the system and spares availability. Various reliability and maintainability parameters are derived from established computer systems, further developed for m o d e m equipment and then considered in relation to the latest computers.
Reliable optoelectronic circuit design. J. BLISS. Semiconductors (1972) (Motorola), p. 17. Two photoelectric systems are described in this article as examples of the design procedure for such circuitry. One operates
T h e reliability of electronic equipment is especially important when such equipment is used in the control of large plant or complex systems. Typically, important plant operational aspects are: (a) the availability requirement; (b) the safety requirement. T h e availability requirement usually demands that the plant must operate continously over a specified minimum percentage of the total specified operating time. U n scheduled plant shutdowns due to equipment failures can be very costly and may involve thousands of pounds per hour in lost production. Availabilities in the range of 90-99 per cent are acceptable in many cases. In contrast, the safety requirement usually demands that the plant must shut down should dangerous conditions begin to arise so as to guard against possible damage to costly plant and possible hazards to the public and the operating personnel. In some applications, fail-dangerous probabilities may need to be in the region of 10-4-10 -7 per year or per operation. A n e w reliability prediction method for hybrid circuits. R. R. BRITTON. Proceedings Internepcon 1972, Brighton, 17-19 October (1972), p. 184. The intrinsic reliability of thick-film hybrid integrated circuits is higher than that of equivalent discrete circuits for several reaons: (1) The number of connections between components is reduced to a minimum. Component leads are eliminated so that only the few connections external to the module are subjected to rigorous assembly processes, such as lead forming. (2) Hybrid assembly processes are fewer and are accurately controlled, generally by automatic machines--screen printer, belt furnace, ultrasonic bonder, etc. (3) The small size and rugged construction gives a high degree of protection from shock and vibration stress. (4) The small size allows homogeneous protection of all circuit components from humidity stress by means of hermetic or plastic packaging. T h e high conductivity of the alumina substrate provides a stable, predictable thermal macro-environment. This paper describes work currently being undertaken at the Product Assessment Laboratories of the Plessey Company. The aim of the work is to provide a technique to enable hybrid manufacturers and users to assess the probability of hybrid circuit failures due to component drift under any relevant stress-life combination.
Effects of test capability on system reliability and availability. G. R. COMPTON,R. S. PRINGLE and P. H. MUEGGLER. IEEE Trans. Reliab. R-21, No. 4, November (1972), p. 239. The impact, on system reliability and availability, of periodic testing with imperfect test equipment is analyzed. T h e proportion of the system tested,