The Complete FDE Cycle

Part of Fetch-Decode-Execute Cycle Ā· Section 7 of 10

DiagramUnit: 3.4 Computer SystemsGCSE
The Fetch-Decode-Execute Cycle 1. FETCH PC ā†’ MAR Address Bus ā†’ Memory Data Bus ā†’ MDR MDR ā†’ CIR PC = PC + 1 2. DECODE Control Unit examines CIR Split into opcode + operand Determine operation type Prepare control signals (No register changes) 3. EXECUTE Perform operation: ā€¢ ALU calculation ā€¢ Data transfer ā€¢ PC change Result ā†’ ACC Repeat billions of times per second! Example: Executing "ADD 5" instruction at address 100 FETCH: ā€¢ PC holds 100 ā€¢ 100 ā†’ MAR ā†’ Address Bus ā†’ Memory ā€¢ "ADD 5" instruction ā†’ Data Bus ā†’ MDR ā€¢ MDR ā†’ CIR (now holds "ADD 5") ā€¢ PC increments: 100 ā†’ 101 DECODE: ā€¢ CU reads "ADD 5" from CIR ā€¢ Opcode: ADD (addition) ā€¢ Operand: 5 (value to add) ā€¢ CU: "Prepare ALU for addition" ā€¢ (No register changes) EXECUTE: ā€¢ ACC currently holds 8 ā€¢ ALU performs: 8 + 5 ā€¢ Result = 13 ā€¢ 13 stored in ACC ā€¢ Cycle complete!

This diagram covers The Complete FDE Cycle within Fetch-Decode-Execute Cycle for GCSE Computer Science. Revise Fetch-Decode-Execute Cycle in 3.4 Computer Systems for GCSE Computer Science with 16 exam-style questions and 12 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 10 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.

Practice questions for Fetch-Decode-Execute Cycle

What does FDE stand for in computer science?

  • A. Find, Delete, Execute
  • B. Fetch, Decode, Execute
  • C. Fetch, Decode, Evaluate
  • D. Format, Decode, Execute
1 markfoundation

Describe the three stages of the FDE cycle.

3 marksstandard

Quick recall flashcards

What does FDE stand for?
Fetch-Decode-Execute
What are the three stages of the FDE cycle?
Fetch, Decode, Execute (repeats continuously)

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