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Even though today's processors are tremendously fast, their performance can be affected by several factors, such as:

• clock speed
• cache size
• number of cores

Clock speed

Clock speed is the number of pulses the central processing unit’s (CPU) clock generates per second. It is measured in hertz (Hz).

The faster the clock speed, the faster the computer is able to run fetch-decode-execute cycles. This means that it can process more instructions in the same amount of time.

CPU clocks can sometimes be sped up by the user. This process is known as overclocking. When the number of pulses per second is increased, more fetch-decode-execute cycles can be performed and more instructions can be processed in a given time. This increases performance, but also requires more power, which results in a greater need for heat dissipation and can strain the life of the battery. Overclocking causes the CPU to work harder and produce more heat, which can lead to long-term damage to the hardware.

Cache

Cache is a small amount of high-speed random access memory (RAM) built directly within the processor. It is used to temporarily hold data and instructions that the processor is likely to reuse. This allows for faster processing as the processor does not have to wait for the data and instructions to be fetched from RAM.

The larger the cache size, the less time a processor has to wait for instructions to be fetched. This improves performance.

Number of cores

A processing unit within a CPU is known as a core. Each core is capable of fetching, decoding and executing its own instructions.

A CPU with more cores can process more instructions in a given time. However, sometimes one core will have to wait for the output from another before carrying out the next phase of the instruction, which can cause a delay.

Multiple cores increase the processor cost. Many modern CPUs are dual-core (two) or quad-core (four) processors. This provides vastly superior processing power.

RISC and CISC

There are two main types of processor:

• reduced instruction set computer (RISC)
• complex instruction set computer (CISC)

RISC processors can process a limited number of relatively simple instructions by breaking each one down into even simpler instructions that can be carried out quickly. Processing simpler instructions requires less circuitry, which consumes less power, so less heat is generated. This makes them ideal for use in smartphones. RISC processors may be used in an embedded system where it is not necessary to process complex instructions and where the instructions are relatively simple and repetitive. They use less power so do not have a need for dedicated cooling systems.

CISC processors are physically larger and can process more complex instructions. They can understand and carry out complex tasks with only a few instructions. Processing complex instructions requires more complex circuitry which needs more power and therefore more heat is generated. Most modern computers use CISC processors.