There are two types of processors for desktop systems – Intel and AMD. You can also find the processors by Cyrix, Rise, Centaur, VIA, SIS, Transmeta, Compaq and other but nowadays these companies cannot compete Intel and AMD.
Processor is a main object for overclocking, so its selection determines if you could increase the working capacity of your computer or not. The selection of processor, in turn, affects the selection of motherboard. If you insert the processor by Intel in the motherboard by Intel, you get good steadily-operating system but almost unoverclockable. You can get some result only from outdated systems with the processors Pentium II or Pentium III. That’s why the manufacturers of a motherboard and chipset must be different, for example, by VIA or SIS, and a motherboard by Abit, Albatron or EPoX.
As a rule, a manufacturer of processors produces a line of similar processors that differ only by the value of multiplying ratio of a system bus. The price of such line is allocated as follows: the lower ratio, the cheaper processor. For example, if it is possible to change the multiplying ratio of a bus at the hardware or software level, the low-cost or cheap processor can be overclocked to the frequency of more expensive processors. But in most cases (especially in modern processors) the multiplying ratio is strictly fixed at the hardware level and cannot be changed. Thus, there is one possibility to overclock your computer – to increase the frequency of FSB. This allows getting the increase of frequency from 10% to 30-35%.
If you buy a processor with the possibility to overclock it in future, keep a close watch on prices on the other models of the same line. The best way is to but a low-cost processor with good fan that has a powerful radiator.