Topic 7 - Fundamentals of Computer Organisation & Architecture

Question 1

Describe the 5 steps of the Fetch stage

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Answer 1

1. The content of the PC is copied to the MAR
2. The content of the MAR is transferred to the main memory by the address bus
3. The instruction is sent from main memory to the MBR by the data bus
4. The PC is incremented by one
5. The content of the MBR is copied to the CIR

Question 2

Describe the 2 steps of the decode stage

Answer 2

1. The contents of the CIR are decoded by the control unit
2. The decoded instruction is split into opcode and operands

Question 3

Describe the 3 stages of the execute cycle

Answer 3

1. Any required data not in the registers is fetched
2. The instruction is carried out
3. The results of any calculations are stored in general purpose registers or main memory

Question 4

Describe the structures of Harvard and Von Neumann architectures?
Where is each typically used?

Answer 4

Harvard - the processor uses two separate main memory locations: one for instructions and another for data.
This is used in embedded systems such as DSP
Von Neumann - instructions and data are stored together in the same memory, sharing busses for fetching instructions and data.
This is used in general-purpose systems like laptops and smartphones

Question 5

What is the stored program concept?

Answer 5

‘Machine code instructions stored in
main memory are fetched and executed serially by a processor that performs arithmetic and logical operations.’