Abstract: A method and system of copying a memory area between processor elements for lock-step execution. At least some of the illustrative embodiments may be a method comprising executing duplicate copies of a first program in a first processor of a first multiprocessor computer system and in a first processor of a second multiprocessor computer system (the executing substantially in lock-step), executing a second program in a second processor element of the first multiprocessor computer system (the first and second processors of the first multiprocessor computer system sharing an input/output (I/O) bridge), copying a memory area of the second program executing in the second processor element of the first multiprocessor computer system to a memory of a second processor element in the second multiprocessor computer system while the duplicate copies of the first program are executing in the first processor elements, and then executing duplicate copies of the second program in the second processors in lock-step.