CPU Performance
- Central Processing Units can have multiple cores
- A dual-core processor has two cores
- A quad-core processor has four cores
- Each core runs separate fetch, decode, execute cycles, independently from one another and at the same time (simultaneously) meaning parallel processing can take place
- Multiple cores enables multitasking (running more than one program at the same time)
- Some programs cannot be split between cores
- The more cores a computer has the more instructions that can be executed per second resulting in better performance
- Each core has a clock speed
- The clock speed is how many instructions the core can execute each second
- The clock speed is measured in Hertz
- Modern cores can execute billions of instructions per second
- A gigahertz (GHz) is a billion instructions per second
- A megahertz (MHz) is a million instructions per second
- A CPU core with a clock speed of 3.4GHz can execute 3.4 billion instructions per second
- Cache is a small amount of memory situated within or close to the CPU with very fast read/write speeds
- It is used for storing frequently used instructions/data, recently used instructions, and instructions that are to be fetched and executed next in a process.
- The impact of increasing the amount of cache is that more data can be stored there and accessed faster than if it was in RAM …which improves the performance of the CPU.
- Double the number of cores does not necessarily mean double the number of instructions executed a second. The cores might have different clock speeds and cache sizes
Worked example
One computer has a single core processor and the other has a dual core processor. Explain why having a dual core processor might improve the performance of the computer
[2]
Any 2 from:
- The computer with the dual core processor has two cores/double the amount of cores [1]
- Parallel processing can take place [1]
- Each core can execute a separate instruction at the same time [1]
- Each core can process instructions independently of each other [1]
Exam Tip
- There are three key factors that affect CPU performance - the number of cores in your CPU, the cache size and clock speed. You need to able to identify these factors and explain how they affect the computer’s performance.
