# Computer Organisation and Architecture

## Student zone

### Further exercises for Computer Organisation and Architecture

Chapter 1

1. For each of the letters of the alphabet, extend the list of acronyms at the end of this book. The added acronyms must be relevant to the subject of this book. Use the Internet and any other text books to help in this task.

2. Section 1.3 was written with systems that use the Intel and equivalent family of processors in mind. Investigate the types of systems that use Motorola processors and write a report that highlights the differences and similarities between these and the Intel based machines.

3. Briefly investigate the Unix or Linux operating system and write a short report to explain the types of user interface that is available with this operating system.

4. A home computer user has a desk top PC, a portable computer and a PDA. Investigate ways in which these can be interconnected so that data may be transferred between them. Document your investigation in the form of a short explanatory leaflet.

Chapter 2

1. Find out what the EBCDIC code is and write a short report that explains the differences between the EBCDIC and ASCII codes.

2. Convert the following negative decimal numbers into one’s and two’s complement form:

(a) -10 (b) -65 (c) -128

3. Investigate the octal code and find out why octal representation of data was used when working with some early main frame computers. Convert the three binary numbers of exercise 4, page 24, into octal.

4. The BCD code on page 20 uses weights of 8, 4, 2 and 1. An alternative BCD code uses weights of 2, 4, 2 and 1. Answer TQ 2.9 using 2,4,2,1 BCD.

5. Carry out research into floating point formats and determine any relative advantages and disadvantages of the various formats.

Chapter 3

1. Section 3.2.3 describes a 2-to-4 decoder.

a) If there are 3 inputs to a decoder how many outputs are there?

b) Draw a circuit for the decoder in (a).

2. Draw a truth table for the R-S flip-flop in figure 3.7. Note that the current value of the outputs provide input for the next value of the outputs.

3. Section 3.4.2 describes a shift register that takes a serial input and produces parallel output. Draw a circuit that has a parallel input and serial output.

4. Determine whether the following pairs of logic expressions are equivalent by creating their truth tables

a) NOT A AND NOT B = NOT (A OR B)

b) NOT A OR NOT C = NOT (A AND C)

c) NOT (B OR C) = NOT B XOR NOT C

d) NOT (A XOR B) = (A AND B) AND (NOT A AND NOT B)

5. Section 3.1 refers to microprocessors containing millions of transistors. Research into the number of transistors in a modern microprocessor such as the Intel Itanium or AMD Opteron.

6. What is the size of the transistors used in the microprocessors in 5?

Chapter 4.

1. The following table shows the program code in the memory of the processor shown in figure 4.1. When the program has finished, what value will be in memory location 8?

• 0: move 5

• 2: sub 7
• 3: store 8
• 4: stop
• 5: 4
• 6: 5
• 7: 3
• 8: 0

2. Write the RTL for the instruction in location 2 in question 1.

3. A processor is rated at 300 MIPS. It has a clock frequency of 900 MHz. Calculate the average number of cycles per instruction.

4. The processor in question 3 uses a four-stage pipeline. It executes a program consisting of 400 million instructions. 12% of the instructions are branch instructions with the branch taking 8% of the time. The branch penalty is two cycles. What speed up is achievable with this processor over that used by a processor with no pipeline.

5. Compare and contrast the use of Branch Prediction, Branch Bypassing and Delayed Branch.

6. Section 4.3.2 refers to level 1 and level 2 cache. Microprocessor based systems are now appearing with three levels of cache. Research into where in the system the three levels of cache are located and typical quantities for each.

Chapter 5

1. Identify the addressing modes used by each of the following instructions:

a) nop

b) jmp 0345

d) sub [0123],[bx + di]

e) mov ah, [bp + 2]

2. Refer to the code in figure 5.15.

a) Determine the number of bytes for each instruction.

b) Use the information in figure 5.14 and table 5.4 to determine the machine code for each of the move instructions in the code. (Check by entering the code into debug.)

3. Convert the following to 32-bit floating point notation:

a) 65536.0625­10

b) -0.000007629394513251110

4. The following are in 32-bit floating point notation. Calculate the fixed point decimal equivalent.

a) 3E58000016

b) 95DC00016

5. The floating point unit in the Pentium processor can also process BCD digits. What would be the result of adding the following two BCD numbers: 8347516 & 3797516?

6. Compare and contrast the operating modes offered by the Pentium processor.

Chapter 6

1. The latest AMD processor has the memory interface on the processor chip rather than in the Northbridge chip. What are the pros and cons of this approach?

2. Research into what memory devices are available for the most recent microprocessors.

3. If cache memory is faster than main memory why isn't all of main memory made up of cache memory?

4. What limits the amount of level 1 and level 2 cache in a system?

5. As there is less cache memory than main memory there can be many main memory blocks potentially mapped to the same cache block. How can the system determine which of the main memory blocks is actually resident in the cache block?

What is meant by locality of reference and how is this used in the design of cache memory?

Chapter 7

1. Draw up a table that shows the cost per KByte of secondary memory. Include hard disks, magnetic tape, floppy disks, CDs and DVDs and any other type of storage devices currently available.

2. Investigate and draw up a short presentation that explains the various types of exchangeable data storage devices currently available with their relative advantages and disadvantages being discussed.

3. Investigate and explain the purpose of the hard disk low level formatting facility provided in most PC CMOS set up facilities.

4. Investigate the technology that uses holographic mechanisms to provide storage, mentioned in chapter 12, and determine its current state of use.

5. Investigate DVD - R, -RW, +R and +RW and write a short report that compares and contrasts these.

Chapter 8

1. Keyboards and mice may be connected to their computers using non-wired methods. Investigate and write a short report that explains these alternative connection methods and provides a discussion on their relative advantages and disadvantages.

2. Devices consisting of a printer, a scanner and a photocopier all combined into one device are becoming popular for use in the home. Investigate and report on the currently available devices. Discuss their suitability for use in small office situations and compare and contrast them, in terms of their cost for consumables, with dedicated printers and photocopiers.

3. Compare and contrast the use of USB and Firewire for connecting peripheral devices to a PC system.

4. The price of inkjet printer cartridges varies considerably, with those for some printers priced at a few pounds each, whilst others are priced at £20 or more each. Investigate this by drawing up a table that shows the various prices against products and attempt to determine why there is such a large price variation. Does the price of the inkjet cartridges relate to the purchase price of the printers?

5. For making a presentation, a device can be used to project what is displayed on the monitor of a PC onto a cinema type screen. Investigate these devices and produce a short report that explains how they work and how they are connected to the PC.

Chapter 9

1. Describe the function of POST and system boot and identify which mode the processor will be left in when the boot processes is completed.

2. What information would you expect to find in a process control block?

3. If mutual exclusivity is not maintained over a printer what may the result be?

4. Explain what is meant by multithreading and compare this to Intel’s Hyperthreading. (Some research will be required for this!)

5. Explain how the principle of locality of reference is used in the design of memory management systems.

6. Research into the file management technique used by NTFS in the Windows operating system.

Chapter 10

1. Explain why there are a number of processors that are a RISC/CISC hybrid and try to find examples.

2. Research on the Internet for sites which contain benchmark information to determine the range of benchmarks available and what they attempt to ascertain.

3. Server products that commonly had RISC processors in them are being replaced by products based on CISC processors. Why might this be? (Research on the Internet for clues.)

Chapter 11

1. The computing facilities of a family living in a house consist of two desk top PCs and a portable computer. There is a scanner and two printers, a colour inkjet and a cheap laser printer. Access to the Internet is via, what is called, a Broadband service.

With the aid of diagrams explain how these devices can be inter-connected such that sharing of the peripheral devices, the file stores of each computer and the Internet access can be achieved.

Explain the function of each device needed to make the inter-connection.

2. A small office has six PCs, two laser printers, a scanner and currently one PC has a connection to an ADSL service, which is used to access the Internet and provide e-mail facilities.Suggest ways in which the PCs can be connected together as a LAN so that complete sharing of all facilities can be achieved.Produce a list of all extra devices that will be needed, together with approximate prices. What security risks are there in the systems suggested?

3. Two employees of the company that has the small office of exercise 2, wish to access the network from their homes. Suggest how this could be done and explain what extra hardware and software would be needed and where this would be located.

4. The use of wireless networks is growing especially in the small business sector. Investigate what is currently available and comment on its suitability for providing network requirements identified in exercise 2.

5. Investigate ways in which the Internet could be used as a means of interconnecting two office sites, 50 miles apart, each of which currently has a small server based LAN comprising eight PCs and a dedicated server. Currently the LANs have no connection to the Internet, but there are normal telephone services available. The amount of inter-site traffic is likely to be small consisting of a few e-mails, but there is going to be a heavy demand for browsing the Internet from all PCs.

Appendix 1

1. Gray code belongs to a class of codes called minimum-change codes. Only one bit in the code group changes when going from one step to the next. The table below lists consecutive binary values and the corresponding Gray code. Produce a circuit that will take the 4-bit binary value as input and output the 4-bit Gray code.

binary gray code

• 0 0000 0000

• 1 0001 0001
• 2 0010 0011
• 3 0011 0010
• 4 0100 0110
• 5 0101 0111
• 6 0110 0101
• 7 0111 0100
• 8 1000 1100
• 9 1001 1101
• 10 1010 1111
• 11 1011 1110
• 12 1100 1010
• 13 1101 1011
• 14 1110 1001
• 15 1111 1000

Appendix 2

1. Executable files have information at the beginning of the file that is not actually executed. Look into what this information is and how it differs between .exe and .com files in MS-DOS.

Exercise 5 in chapter 5 asks for a program to calculate the area of a circle. Now try a program that will calculate the circumference of a circle radius 32768.625.