Abstract: A method and system of presenting an interrupt request to processors executing in lock step. At least some of the illustrative embodiments are computer systems comprising a first processor configured to execute a program, a second processor configured to execute a duplicate copy of the program in lock step with the first processor, and a logic device coupled to the processors. The logic device is configured to present an interrupt request to the processors when the processors are at substantially the same computational point in the program.

Abstract: A method and system of determining the execution point of programs executed in lock step. At least some of the illustrative embodiments are computer systems comprising a first processor that executes a program, and a second processor that executes a duplicate copy of the program in lock step with the first processor. After receipt of a duplicate copy of an interrupt request by each processor, the first processor determines the execution point in its program relative to the execution point of the duplicate copy of the program executed by the second processor.

Abstract: A method and system of bringing processors to the same computational point. At least some of the illustrative embodiments are computer systems comprising a first processor executing a program, a second processor executing a duplicate copy of the program (but at different computational points in the program), and a shared main memory coupled to the first and second processors. When the processors each receive duplicate copies of an interrupt request, the processors are configured to bring their respective programs to the same computational points prior to servicing the interrupt request.

Abstract: A method and system of executing duplicate copies of a program in lock step. Some illustrative embodiments are a computer system comprising a first processor executing a program, a second processor executing a duplicate copy of the program (the first processor and second processor executing their respective programs in lock step), a logic device coupled to the processors, and a shared device coupled to the processors through the logic device. The first processor presents to the logic device a first operation involving the shared device, and the second processor does not present an operation, or presents an operation that does not match the first operation. The logic device obtains a second operation from the second processor that matches the first operation, and wherein a single operation that matches the first and second operations is presented to the shared device.