CPU and System Performance

You should be able to…

  • Explain how common characteristics such as clock speed, cache size and number of cores affect CPU performance

CPU Characteristics and Performance

There are many factors that can impact the performance of the CPU in your computer. You need to have an understanding about how the following:

Clock Speed

This refers to how many fetch, decode and execute cycles the CPU can perform in a given time. This is usually given per second (Hertz, Hz) and modern Central Processing Units are usually quoted in Gigahertz (GHz). Giga refers to 1 billion in Computer Science so a CPU that has a clock speed of 3 GHz could perform 3 billion fetch, decode and execute cycles every second. So in simple terms the higher the clock speed the faster the CPU will run.

Cache Size

Cache is very fast memory that is on the CPU. It is slower than registers but faster than RAM. It stores instructions that are commonly used by the CPU. This type of memory is expensive in comparison to RAM and usually comes in different levels. L1, L2 and L3. These decrease in speed but increase in memory size and we go from 1 to 3. So L1 cache is the fastest but with the smallest capacity and L3 cache is the slowest but has the most memory.

Number of Cores

The more cores that a CPU has the more instructions it can carry out at one time. It essentially means that the CPU is better at multitasking. This means a dual or quad core processor would deal with the demands of having many applications running at the same time better than a single core processor. Most Central Processing Units have 4 or more cores today.

You need to have notes in your book on the following things:

  • Clock Speed
  • Number of Cores
  • Cache Size