Cambridge Syllabus Notes

Computer Architecture Overview

In a computer, computer architecture is like the blueprint that tells every part how to work together. Think of it as the rule book for the whole machine.

The Role of the CPU

What Does the CPU Do?

🧠 The Central Processing Unit (CPU) is the brain of the computer. It:

Fetches instructions from memory.
Decodes what the instruction means.
Executes the instruction (e.g., adds numbers).
Stores the result back in memory.

This cycle is called the fetch‑decode‑execute cycle and repeats millions of times per second.

Why is the CPU Important?

The speed of the CPU determines how fast a computer can run programs. It’s like how fast a runner can sprint in a race.

What is a Microprocessor?

A microprocessor is a single chip that contains the CPU and a few other essential components. Think of it as a mini‑brain that can fit inside a phone, laptop, or even a microwave oven.

🔧 Key features:

All CPU functions (ALU, control unit, registers) on one chip.
Can be combined with memory and I/O controllers to make a complete system.
Smaller, cheaper, and uses less power.

CPU Components

Component	Function
ALU (Arithmetic Logic Unit)	Performs maths and logical operations.
Control Unit	Tells the CPU what to do next.
Registers	Fast storage for data the CPU is currently using.
Cache	Very fast memory that stores frequently used data.

Exam Tips

Tip 1: Remember the fetch‑decode‑execute cycle – it’s a core concept in many exam questions.

Tip 2: When asked about a microprocessor, highlight that it’s a single chip containing the CPU and key components.

Tip 3: Use the analogy of a brain (CPU) and a micro‑brain (microprocessor) to explain the difference clearly.

Tip 4: Draw a simple diagram of the CPU components (ALU, control unit, registers, cache) if the question allows.

Tip 5: Show understanding of how speed (clock rate) affects performance: Higher clock rate = more instructions per second.

Understand the role of the CPU and the meaning of microprocessor