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Cork Institute of Technology
Bachelor of Science in Computing in Information Technology
Support - Award
(NFQ Level 7)
Autumn 2006
Computer Organisation
(Time: 3 Hours)
Answer Question 1 Plus Any Three of the Remaining Questions
Examiners: Dr. J. Twomey Mr. J. Greenslade Mr. J. Walsh
Q1. Attempt Any Five of the Following Seven Sections:-
(i) Describe the function of 'pipes' in UNIX and what is the notation used for 'piping'. (5 marks) (ii) Compare “CISC” with “RISC” computing. (5 marks) (iii) Describe the essential features of IPv6. What are the main advantages of IPv6 over IPv4? (5 marks) (iv) Compare the Different Configurations in Multiprocessing outlining both their advantages and disadvantages. (5 marks) (v) Explain the terms 'Internal Fragmentation', 'External Fragmentation' and 'Compaction'. (5 marks) (vi) What is 'Thrashing' and how does the OS detect 'thrashing'? (5 marks) (vii) Explain 'paging' and what is the function of the 'modified' bit? (5 marks)
Q2. (a) What is the 'Principle of Locality of Reference'? (5 marks) (b) In a computer process, Arithmetic Logic Unit (ALU) operations occur for 40% of the time, Branching occurs for 20% of the time and Data Activity for 40% of the time. Assume that each of the above three activities has a CPI (cycles per instruction) of one cycle. The CACHE Miss Rate for both the ALU and Branching is 4% for each activity and for the Data Activity it is 8%. Assume that the 'Miss' penalty in each case is 30 cycles. How much faster would the overall process run if there were no CACHE misses. (14 marks) Hint choose an Instruction Count(IC)=1000 and an arbitrary value for the Clock Cycle Time. (c) In a pipelining environment the times involved in each of five stages are 9ns, 7ns, 7ns,10ns and 6ns respectively. Assuming that pipelining adds 0.5ns of overhead determine the 'SpeedUp' versus a single-cycle data-path? (6 marks)
Q3. (a) What is a 'Semaphore' and when is it used? (3 marks) (b) In a multiprocessing environment, explain the operation of Test-AND-Set (TAS). Compare the operation of TAS with the process used in Wait-AND- Signal. (4 marks) (c) Define the P and V functions and what operations do they perform? (4 marks) (d) In the following table complete the missing portions assuming s =1 in state ‘0’? (9 marks) State No Calling Process Operation Running Process S Value 0 1 1 P1 P(s) 2 P1 V(s) 3 P2 P(s) 4 P3 P(s) 5 P3 P(s) 6 P2 V(s) 7 P? ?(s)
(e) Determine the advantage of Parallel Processing over Serial Processing with reference to the following expression:- (5 marks) X = (4J+KLM)*I
Q6. (a) What are the features of a Sequential File and an Index Sequential File. Give an example of a suitable application for each type. (5 marks) (b) How does DES and PKE encryption systems function and explain their relative advantages. (5 marks) (c) What are the main security threats to a computer system? Outline some of the actions needed to minimize these threats. (6 marks) (d) What is the difference between a WORM, VIRUS and a Trojan Horse. (4 marks) (e) A computer system has a MTBF (Mean Time Between Failures) of 3000 hours and a Mean Time To Repair (MTTR) of four hours. Determine the availability and estimate the reliability of the system over an 3 hour period. You may use the approximate Nickel expression for calculating the reliability. (5 marks)
