Abstract: A method detects a defective module in a signal processing apparatus having modules capable of communicating with each other. The method includes the step of incrementing the number of occurrences of communication failure for each module relevant to communication where a communication failure has occurred, upon occurrence of the communication failure, while monitoring communications among the modules. The method further includes the step of detecting a defective module based on the number occurrences of communication failure for each module incremented in the step of incrementing the number of occurrences of communication failure.

Abstract: In the master control unit, updated information is transferred to a slave control unit and a coherence of information between the master control unit and the slave control unit is periodically checked, thereby eliminating a difference of the internal information of the two units which execute a control, a status monitor, and a maintenance of a computer system in an on-line manner and guaranteeing the coherence. When the master control unit recognizes a difference between the information for a predetermined time or more, the slave control unit is halted and the information of the master control unit is made effective. With respect to an abnormality of the master control unit, the master control unit halts by itself. In this instance, the slave control unit is shifted to the master status and takes over the process.

Abstract: Upon detection of service interruption, the power supply unit gives a notice of the occurrence of service interruption to the processor unit to instruct save operation from the memory unit to the storage device, then instructs power disconnection to the second power supply section to discontinue supply of power, and continues supply of power from the power supply section to the memory unit and the storage device for save operation. The power supply control unit gives an advance notice of power disconnection to the memory unit prior to the instruction of power disconnection to the second power supply section to start save operation from the memory unit to the storage device, and upon the lapse of a prescribed period of time from the advance notice, instructs power disconnection of the second power supply section. Upon receipt of an end notice of save operation from the memory unit, the power supply control unit instructs the first power supply section to disconnect to discontinue supply of power.