1.1.1.3 Factors affecting CPU Performance

Question 1

What are the factors affecting CPU performance?

Answer 1

• Clock speed
• Number of cores
• The amount of cache memory
• The type of cache memory

Question 2

What is Clock Speed?

Answer 2

• The clock speed is determined by the system clock.
• This is an electronic device which generates signals, switching between 0 and 1.
• Clock speed is the frequency at which the system clock generates these signals.
• All processor activities begin on a clock pulse, and each CPU operation starts as the clock changes from 0 to 1.
• The clock speed is the time taken for one clock cycle to complete.

Question 3

What is a Core?

Answer 3

• A core is an independent processor that is able to run its own fetch-execute cycle.
• A computer with multiple cores can complete more than one fetch-execute cycle at any given time.
• A computer with dual cores can theoretically complete tasks twice as fast as a computer with a single core.
• However, not all programs are able to utilize multiple cores
  efficiently as they have not been designed to do so, so this is not always possible.

Question 4

What is Cache?

Answer 4

• A small and fast but expensive memory in the CPU used to store instructions and data that are accessed regularly.

Question 5

Explain Cache.

Answer 5

• Cache memory is the CPU’s onboard memory.
• Instructions fetched from main memory are copied to the cache, so if required again, they can be accessed quicker.
• As cache fills up, unused instructions are replaced.

Question 6

What are the types of cache?

Answer 6

• Level 1 Cache:
  Very fast memory cells with a small capacity. (2-64KB)
• Level 2 Cache:
  Relatively fast memory cell, with a medium sized capacity. (256KB-2MB)
• Level 3 Cache:
  A slower memory cell, but has a much larger capacity.