CPU Performance | 1.2 | OCR GCSE Computer Science

12 flashcards

What are the 3 main factors that affect CPU performance?: - cache size - clock speed - number of cores
Clock: A component that produces regular electrical pulses.
Clock speed: The number of FDE cycles the CPU can complete per second. 4 Hz = 4 FDE cycles per second. 4 MHz = 4 million FDE cycles per second. 4 GHz = 4 billion FDE cycles per second.
Why does a higher clock speed increase CPU performance?: 1. As it means more fetch-decode-execute cycles can be completed per second. 2. This means more instructions can be executed in the same amount of time - so tasks are completed faster.
Cache Memory: Fast, temporary storage inside / close to the CPU that stores frequently accessed data and instructions.
How many levels are cache split into?: 3 levels - L1, L2, L3 - Each level being larger and slower than the previous one.
Why does larger cache size increase CPU performance?: The larger the cache size, more frequent data can be stored, so they do not have to be stored further away, so data can be accessed faster.
Why are frequently accessed data and instructions stored in cache?: Because it is closer to the CPU than RAM, so it is faster to access.
Core: - An individual processing unit within the CPU. (containing components such as CU, ALU, registers and cache). - Each core can independently perform the FDE cycle.
1, 2, 4 and 8 cores are called...?: 1 core: single-core 2 cores: dual-core 4 cores: quad-core 8 cores: octa-core
How does number of cores increase CPU performance?: The more cores a CPU has, the more instructions it can carry out.
With cores, how may CPU performance NOT improve?: - If one core must wait for another core to complete its task. - If certain software are not built to have multiple cores, so they don't benefit from additional cores.