What It Is:
The CPU operates on a "clock" that ticks at a regular rate. Clock speed measures how many times per second the clock ticks. Each tick is called a cycle.
Measured In:
- Hertz (Hz): 1 cycle per second
- Megahertz (MHz): 1 million cycles per second (1,000,000 Hz)
- Gigahertz (GHz): 1 billion cycles per second (1,000,000,000 Hz)
- Example: A 3.2 GHz CPU ticks 3.2 billion times every second!
How It Affects Performance:
- Higher clock speed = more instructions per second
- The CPU can complete more FDE cycles in the same time
- Example: 4 GHz CPU is roughly twice as fast as 2 GHz CPU (same architecture)
- BUT: Higher speed = more heat and power consumption
Important Limitation:
Not all instructions take the same number of cycles! A simple ADD might take 1 cycle, but a MULTIPLY might take 3-4 cycles. A DIVIDE could take 10+ cycles. So doubling clock speed doesn't always double real-world performance.
This key facts covers Factor 1: Clock Speed (Measured in GHz) within CPU Performance for GCSE Computer Science. Revise CPU Performance in 3.4 Computer Systems for GCSE Computer Science with 15 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 8 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for CPU Performance
What does clock speed measure in a CPU?
Describe three factors that affect CPU performance.