Abstract: A Fault-Tolerant Multi-Computer System for control applications is disclosed. The system has a plurality of Computers (10a-10n), each having an assigned set of tasks which it is capable of executing. No one Computer in the system acts as a master and no one Computer executes all of the tasks. Communication between the Computers is by individual communication links (16, 18, 20) over which each Computer sends information directly to all other Computers in the system. Each Computer comprises an Applications Computer (100) and an Operations Controller (200). The Operations Controller receives messages over the communication links and selects, from the assigned tasks, the tasks to be performed by the associated Applications Computer. Each Operations Controller includes a fault handler which checks the messages received from the other Computers. The fault handlers send and receive error messages, over the communication links, to assist in the identification of a faulty Computer.

Abstract: An operations controller for each computer in a multiple computer system is disclosed. Each operations controller controls the operations of its associated computer, so that all of the computers cooperate to perform system functions in a fault-tolerant manner. Each operations controller comprises a fault handler (204), a scheduler (206), a task communicator (208), plus a transmitter (212) and requisite receivers (202) which receive and send messages to all the other computers in the system. The fault handler (204) checks each message received and decides which computers are operating correctly and which are faulty. A scheduler (206) selects each task its own computer will execute, from the tasks assigned to its own computer. A task communicator (208) assembles the data values required for the execution of the selected task, and forwards this data to the computer for execution.

Abstract: A scheduler for selecting and scheduling the tasks to be executed by a computer in a multiple computer system is disclosed. One scheduler is associated with each computer, and the schedulers coordinate their operation by sending and receiving messages. Each scheduler comprises a status table (604) storing the status of each task assigned to its computer, and a scheduling status table (608) storing the tasks recently selected for execution by the computer. The scheduler further includes a record data ready module (600) which records in the status table (604) the reception of the data variables required for the execution of each task. A completed task recorder (612) records which tasks have been executed by itself or any other computer in the system. An unselected/selected task recorder records the selection and unselection of tasks by other computers. A task unselector records the tasks which have been unselected by itself.