1. Field of the Invention
The present invention relates to a computer system having a multiprocessor construction, more particularly to a system for controlling the transfer of commands between processors in a multiprocessor system.
2. Description of the Related Art
One of the major methods for forming a computer system is to tie in a plurality of central processors, input/output processors, and the like to a common main memory unit. Such a system is called a multiprocessor system.
Such a multiprocessor system requires means for compulsory synchronization of the control operation between processors or the ability to directly transmit command information and response information therefor between processors for the control of startup at the start of system operation, control by one processor over the initialization, start, stop, etc. of another processor when the other processor is malfunctioning, etc.
For example, the central processors in multiprocessor systems are subject to what are called "signal processor commands", by which they transfer commands to other processors for the above-mentioned purpose. When executing such a command, they transfer command codes and parameters specified by the command to a designated processor and receive response information therefrom.
The response information includes the state of receipt of the commands and, when the commands are not received, information allowing determination of the state of the specified processor.
Further, when a desired kind of command is executed, information summarizing the results of executing, etc. is set as a condition code. The condition code of a signal processor command is mainly formed based on the above-mentioned response information.
For such transfer of information between processors, conventional systems, have been provided with information transfer paths (wires) directly connecting the processors for every combination of two processors.
Most conventional multiprocessor systems consist of two central processors. Advances in electronics technology, however, have made an increased number of the central processors more practical. A multiprocessor system having an increased number of processors should preferably be controlled by a method different from the conventional method and which different method is appropriate for information transfer between a large number of processors for communication of common information between the processors.
That is, in a method for control of a conventional system, the number of the information transfer lines increases in proportion to the square of the number of the processors and the scale of the control circuit provided in each processor increases in proportion to the number of the processors. Therefore, the scale of the overall system increases in proportion to the square of the number of the processors. This causes problems in economy and reliability.