Abstract: Aligning execution point of duplicate copies of a user program by exchanging information about instructions executed. At least some of the exemplary embodiments may be a method of operating duplicate copies of a user program in a first and second processor, allowing at least one of the user programs to execute until retired instruction counter values in each processor are substantially the same, and then executing a number of instructions of each user program. Of the instructions executed, at least some of the instructions are decoded and the inputs of each decoded instruction determined (the decoding substantially simultaneously with executing in each processor).

Abstract: A method and apparatus to insert special instruction. At least one of the illustrative embodiments is a method comprising converting a first representation of a computer program to a second representation, and inserting into the second representation a special instruction not needed to implement functionality in the first representation. The special instruction gives duplicate copies of the computer program executed in different processors an opportunity to service external asynchronous interrupts.

Abstract: Aligning execution point of duplicate copies of a user program by exchanging information about instructions executed. At least some of the exemplary embodiments may be a method of operating duplicate copies of a user program in a first and second processor, allowing at least one of the user programs to execute until retired instruction counter values in each processor are substantially the same, and then executing a number of instructions of each user program. Of the instructions executed, at least some of the instructions are decoded and the inputs of each decoded instruction determined (the decoding substantially simultaneously with executing in each processor).

Abstract: A method and system of aligning execution point of duplicate copies of a user program by exchanging information about instructions executed. At least some of the exemplary embodiments may be a method comprising operating duplicate copies of a user program in a first and second processor, allowing at least one of the user programs to execute until retired instruction counter values in each processor are substantially the same, and then executing a number of instructions of each user program. Of the instructions executed, at least some of the instructions are decoded and the inputs of each decoded instruction determined (the decoding substantially simultaneously with executing in each processor).

Abstract: A method and system of aligning execution point of duplicate copies of a user program by copying memory stores. Some of the exemplary embodiments may be a method comprising aligning the execution point of duplicate copies of a user program executed in a first and second processor by copying only data of memory stores performed by the user program in the first processor from a memory of the first processor to a memory of the second processor, and copying the register state of the user program from the first processor for use by the second processor.

Abstract: A system and method for automatically checkpointing a primary computer process to a backup computer process is disclosed. The system and method automatically convert a non-fault tolerant computer program into a fault tolerant computer program. The system includes multiple CPUs, a communications link between the CPUs and a user interface device, such as a terminal, workstation, or PC. A special layer of code forms an interface between the operating system for each CPU and the application programs running on the CPUs. For each process, running on one of the CPUs, the interface automatically creates a duplicate backup process on another CPU. The interface handles synchronizing communications between the original or primary process and the backup process, and suppresses or otherwise prevents or inhibits output from the backup process.