CPU & Fetch-Execute Cycle
Understand how the processor runs every program
What You'll Learn
- Purpose of the CPU - Why every computer needs a processor
- CPU Components - Control Unit, ALU, Cache, and Registers
- Fetch-Execute Cycle - How instructions are processed
- Tracing - Follow the cycle step by step
- CPU Performance - Clock speed, cache size, and cores
- Embedded Systems - Dedicated computers in everyday devices
Key Vocabulary
Inside the CPU
CPU
Control Unit
Coordinates operations
ALU
Does calculations
Registers
PC | MAR | MDR | ACC
The CPU contains the Control Unit, ALU, and Registers working together
The Fetch-Execute Cycle
Every instruction goes through these four stages:
1. FETCH
Get the next instruction from RAM
2. DECODE
Work out what the instruction means
3. EXECUTE
Carry out the instruction
4. STORE
Save the result
This cycle repeats billions of times per second!
Activities
Learn
CPU components, Von Neumann architecture, and the fetch-execute cycle (OCR J277)
Predict
Look at scenarios and predict what the CPU will do
Trace
Follow the fetch-execute cycle step by step
Match
Classify registers as data or address, and match definitions
Sequence
Put the fetch-execute stages in the correct order
Quiz
Test your understanding with multiple choice questions
CPU Performance
What makes one CPU faster than another? Understand the three key factors.
Embedded Systems
The hidden computers in everyday devices - from washing machines to cars.
Why Does This Matter?
Understanding the CPU helps you:
- Choose better hardware - Know what CPU specs actually mean
- Debug programs - Understand why code runs the way it does
- Pass your exams - This is a key GCSE and A-Level topic!
- Think like a computer scientist - See the big picture of how computers work