Hitachi, Ltd.

Hitachi Information Control Systems, Inc.

Naoto Miyazaki

Yoshihiro Miyazaki

Shinichiro Yamaguchi

Tetsuaki Nakamikawa

Shin Kokura

Yuuichiro Morita

Koji Matsuda

Soichi Takaya

Nobuo Akeura

Satoru Kayukawa

Kazuhiro Hyuga

A multiplexed computer system allows memory accessing by a processor, a peripheral equipment or a like apparatus even during execution of memory copying to improve the processing performance during on-line maintenance. To this end, the multiplexed computer system includes a plurality of processing units which effect the same operation in synchronism with each other. Each of the processing units includes a copy processor register for designating a processor to read out contents of a memory unit, a memory copy control unit for transferring copies of the stored contents of the memory unit and data to be written into the memory unit in the same order as that of accesses to the memory unit of the other processing unit, a copy mode flag indicating that memory copy processing for making the stored contents of the memory unit of the self system and stored contents of the memory unit of the other processing unit coincide with each other is proceeding, and a copy task flag indicating that the processor is reading out, during memory copying processing, the stored contents of the memory unit.

Multiplexed computer system

A multiplexed computer system allows memory accessing by a processor, a peripheral equipment or a like apparatus even during execution of memory copying to improve the processing performance during on-line maintenance. To this end, the multiplexed computer system includes a plurality of processing units which carry out the same operation in synchronism with each other. Each of the processing units includes a copy processor register for designating a processor to read out contents of a memory unit, copying circuits which transfer copies of the stored contents of the memory unit and data to be written into the memory unit in the same order as that of accesses to the memory unit to a memory unit of another processing unit, a copy mode flag indicating that memory copying processing for making the stored contents of the memory unit of the self system and stored contents of the memory unit of the other processing unit coincide with each other is proceeding, and a copy task flag indicating that the processor is reading out, during memory copying processing, the stored contents of the memory unit.

Multiplexed computer system with the capability to copy data from one

A method of verifying operation concurrence in maintenance/replacement of twin CPUs employed in a dual-CPU computer wherein a replacement CPU with an initial fault may have been installed by mistake during on-line maintenance/replacement work and a system therefor are disclosed whereby a failure which, without the method and the system, would occur due to the initial fault of the replacement CPU during a dual subsystem synchronous operation carried out thereafter by the computer can be prevented from entailing a system down on both the subsystems.

Method of and system for verifying operation concurrence in

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Hitachi, Japan

Naoto Miyazaki