To get maximum reliability and efficiency a mode of function called as symmetric multiprocessing is used. In essence, with SMP any program or threads can be given to any processor. Symmetric multiprocessing (SMP) adds a multiprocessor computer hardware structure where two or more identical programs are connected to a single shared main storage and are controlled by a single Operating System instance. Most common multiprocessor machines today need SMP structure. In the case of multi-core processors system, the SMP architecture relay to the cores, acting them as separate processors.