Factors Affecting CPU Performance
Computer Science: OCR GCSE, topic 1.1.4
Factors Affecting CPU Performance
Not all Central Processing Units (CPUs) will execute code at the same speed. Some processors will be faster than others depending on the following factors:
Clock speed
- The CPU's clock sends a pulse at fixed intervals to trigger the next stage of the fetch, decode, execute (FDE) cycle.
- The higher the clock speed, the more pulses are sent per second, so more FDE cycles can be completed in the same amount of time.
- Clock speed is measured in Hertz (Hz).
- Modern CPU's are measured in GHz. They perform billions of FDE cycles per seconds.
Cores
- Each core of a CPU is capable of processing one FDE cycle at a time.
- Each core has its own Control Unit (CU), special registers, and Arithmetic and Logic Unit (ALU), but the cores share access to cache and main memory.
- Multiple cores allow a CPU to process multiple FDE cycles at the same time.
Cache memory
- Cache memory is a small amount of very fast memory inside the CPU.
- In comparison to the cache, accessing the Random Access Memory (RAM) is a very slow operation.
- By storing frequently accessed data and instructions in cache memory we can avoid the process of accessing the RAM.
Negatives
- These components can lead to negative consequences:
- Clock speed: overclocking & generating too much heat.
- Cores: specific software may need to be created.
- Cache: if it is too big, it can spend just as much time accessing the correct data/instruction as if those were in main memory.
Test yourself on Factors Affecting CPU Performance
Which of the following will increase CPU performance?
Which of its three factors is most important for a high performance CPU?
Think of an answer, and then check the answer to compare it to your own.