The CPU and the fetch-execute cycle

Overview

The Von Neumann architecture, the ALU, control unit, clock, registers and buses, how clock speed, cores and cache affect performance, and the fetch, decode and execute stages.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is the Von Neumann architecture?

   Model answer

   The Von Neumann architecture is a computer design in which program instructions and data are stored together in main memory. The CPU fetches both from that memory.

2. 2

   What is the role of main memory in the Von Neumann architecture?

   Model answer

   Main memory holds the programs and data currently in use. The CPU reads instructions and data from main memory and writes results back to it.

3. 3

   What does the arithmetic logic unit (ALU) do?

   Model answer

   The ALU carries out arithmetic such as addition and subtraction. The ALU also performs logical operations and comparisons, such as testing whether one value is greater than another.

4. 4

   What does the control unit do?

   Model answer

   The control unit decodes instructions and sends control signals to the other components. The control unit coordinates the fetch-execute cycle and the movement of data around the CPU.

5. 5

   What is the role of the clock in a CPU?

   Model answer

   The clock sends out a regular electrical pulse that keeps the CPU's components working in step. Each tick triggers the next step of processing.

6. 6

   What is a register?

   Model answer

   A register is a very small, very fast memory location inside the CPU. Registers hold the instruction or data currently being worked on.

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