The performance or speed of a processor depends on e.g. the clock rate and the Instructions Per Clock (IPC), which together are the factors for the Instructions Per Second (IPS) that the CPU can perform. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches, whereas realistic workloads consist of a mix of instructions and applications, some of which take longer to execute than others. The performance of the memory hierarchy also greatly affects processor performance, an issue barely considered in MIPS calculations. Because of these problems, various standardized tests such as SPECint have been developed to attempt to measure the real effective performance in commonly used applications.
Processing performance of computers is increased by using multi-core processors, which essentially is plugging two or more individual processors (called cores in this sense) into oneintegrated circuit. Ideally, a dual core processor would be nearly twice as powerful as a single core processor. In practice, however, the performance gain is far less, only about fifty percent, due to, e.g. imperfect software algorithms and implementation