NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
SEPTEMBER 2020 EXAMINATION

CIT309 – Computer Architecture

Credit: 3 units

TIME ALLOWED: 2½ Hours

INSTRUCTION: Answer Question 1 and any other FOUR (4)

Questions 1

a) Describe the key concepts upon which the von Neumann architecture is based. (6 marks)

b) What is the difference between computer architecture and computer organization? (4 marks)

c) A pipeline is designed with 5 stages having execution times respectively as 3ns,5ns,4ns and 5ns. How much time will it take to execute 2000 instructions? (2 marks)

d) Name two RISC and two CISC processors. Explain five main characteristics of RISC processors. (6 marks)

e) What is virtual memory? Explain the need for virtual memory. (2 marks)

f) What is the difference between static and dynamic pipelines? (2 marks)

QUESTION TWO

a) Describe how the instruction cycle code (ICC) designates the state of the processor in terms of which portion of the cycle it is in. (4 marks)

b) Draw the flowchart that defines the complete sequence of microoperations, depending only on the instruction sequence and the interrupt pattern. (8 marks)

QUESTION THREE

a) Define the basic elements of a processor. (4 marks)

b) Describe the micro-operations that the processor performs. (4 marks)

c) Determine the functions that the control unit must perform to cause the microoperations to be performed. (4 marks)

QUESTION FOUR

a) Draw a general model of the control unit showing all the inputs and outputs. (5 marks)

b) Describe the inputs and outputs of the unit. (7 marks)

QUESTION FIVE

a) Briefly define types of parallel processing systems. (7 marks)

b) Draw the model of the Symmetric Multiprocessor system. (5 marks)

QUESTION SIX

a) Using Boolean algebra techniques, simplify the expression: AB + A(B+C) + B(B+C) (5 marks)

b) Determine the binary values of the variables for which the following product-of-sums (POS) is equal to 0: (A + B + C + D) (A + BÌ… + CÌ… + D) (AÌ… + BÌ…+ CÌ… + DÌ…) (6 marks)

c) What is parity bit. (1 mark)