The CPU - EduqasFactors affecting CPU performance

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.

Levels of cache

The CPU uses a multi-level cache hierarchy of Level 1 (L1), Level 2 (L2) and Level 3 (L3) caches, which improves performance by bridging the operating speed between the central processing unit (CPU) and main memory.

An analogy would be to think of:

• L1 as a pocket in which items (such as a smartphone) are kept that need to be accessed quickly and readily
• L2 as a bag where items are needed less often (for example books)
• L3 as a school locker where things could be placed that are needed later on.

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.