Hitachi, Ltd.

Hitachi Process Computer Engineering, Inc.

Ryokichi Yoshizawa

Tomoaki Nakamura

Shigenori Kaneko

Hiroshi Ohno

Toshiaki Arai

Tomoki Sekiguchi

Manabu Yamauchi

Naoshi Kato

Takeshi Miyao

Hidebumi Miyata

An inter-OS control software for switching OS's in operation executed on a single CPU is installed, and plural OS's are made alternately executed. A control program is executed exclusively on one OS, which controls the controlled apparatus. A supervisory control program and a development environment program are executed on another OS, and a memory space is divided so as to make no effect for the operation of the control program. A higher real-time performance and reliability can be established with a single CPU architecture.

Multiple operating system control method

A computer system and method for enabling memory expansion without shutting off the computer system are disclosed. The computer system has a dual memory configuration and supports memory insertion and extraction while being on-line. The memory content of one system may be copied to the memory of another system according to a predetermined priority or after a predetermined delay. Memory may be used efficiently during the insertion or extraction by securing a status management table expansion area in an expanded portion of memory. Memory may be expanded in computer systems that do not have an open memory slot by replacing the installed memory with a memory having a larger capacity.

Computer system including a dual memory configuration which supports

A main memory managing arrangement involves allotting a request program to one of three distinct areas of main memory by looking in an area managing table which stores head addresses and the capacities of the respective areas. The areas allocated in main memory correspond to a single OS area, a single first class program area and a single second class program area. An empty page managing table is also provided for indicating the presence or absence of an empty area conformable to a request in an allocated area. A request program is allocated to the allocated area when the presence of the empty area of required capacity is determined. The memory capacity for a resident program can be assured independently of the memory capacities for other programs to enhance reliability conformable to real-time process computers.

Main memory managing method and apparatus in which main memory is

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Hitachi, Japan

Ryokichi Yoshizawa