The CPU is the brain of the PC and Intel processors continue to rule the roost. Retail CPUs are installed in the motherboard inside a desktop PC. There are many grades of Intel desktop CPU from entry-level models to high-end models, including some that can be overclocked for additional performance. Those looking for a performance PC ought to make a beeline for Intel Core i5, Core i7 and Core i9 processors, with the latter offering staggering performance that makes a mockery of benchmarks and multi-threaded applications. Make sure you select a compatible motherboard for your chosen CPU.