Design of a diagnosable and fault-tolerant input/output controller

The paper describes the design of a diagnosable and fault tolerant input/output controller. The approach used is to follow an initial design effort by a detailed analysis of the organization of the system and its environment. Based on this analysis, modifications are made on the system and its environment to get the desired performance. For the interface controller under consideration, it is seen that its diagnosability and fault-tolerance can be improved significantly by introducing a minor amount of redundancy into the system. The environment which in this case is predominantly a CPU or a channel is modified only to the extent that a nominal amount of software is added and the existing software modified. The overall effect of these modifications results in a system which achieves the reliability comparable to that of duplication but for a redundancy of approximately 30 percent.