As the most important component of a computer system, it is important that the CPU be built with considerable resilience, so that it does not power down when the system is used for extended periods of time. Most CPUs are made with silicon. This is a semiconductor metal. CPUs tend to get very warmed up since all functions of the hardware take place inside it, and while there are internal ventilation and filtration systems, it needs to be made with a material that has a high resistance to heat.