Nowadays almost every computer is made of more than one microprocessor, smaller computers in the form of multicore processors, and the bigger ones usually contain several processors. In this paper my aim is to: describe the development of microprocessors since their invention in 1971 up to present day, explain the architecture and the way they operate, explain the memory hierarchy of operating systems and present future challenges to overcome in the further development of microprocessors. Also listed are the techniques used to enhance microprocessor performances, ways they can be influenced and how they are measured. The paper further explains the support for the operating system through processes, threads and interruptions. The end discusses new generation architectures developed by Intel corporation: Intel Core Duo and Intel Core i7-990X.