ca question bank

8/7/2019 ca question bank

1/67

UNIT I

PART-A

BASIC STRUCTURE OF COMPUTERS

1.What is cache memory?

The small and fast RAM units are called as caches. When the execution of an instruction calls for data located in the main

memory, the data are fetched and a copy is placed in the cache. Later if the same data is required it is read directly from t hecache.

2. What is the function of ALU?

Most of the computer operations (arithmetic and logic) are performed in ALU .The data required for the operation is brought

by the processor and the operation is performed by the ALU.

3. What is the function of CU?

The control unit acts as the nerve center, that coordinates all the computer operations. It issues timing signals t hat governsthe data transfer.

4. What are basic operations of a computer?

The basic operations are READ and WRITE.

5. What are the registers generally contained in the processor?

MAR-Memory Address Register

MDR-Memory Data Register

IR-Instruction Register

R0-Rn-General purpose Registers

PC-Program Counter

6. What are the steps in executing a program?

1.Fetch

2.Decode

3.Execute


2/67

4.Store

7. Define interrupt and ISR?

An interrupt is a request from an I/O device for service by the processor. The processor provides the requested service byexecuting the interrupt service routine.

8. Define Bus?

A group of lines that serves as a connecting path for several devices is called a bus.

9. What is the use of buffer register?

The buffer register is used to avoid speed mismatch between the I/O device and the processor.

10. Compare single bus structure and multiple bus structure?

A system that contains only one bus(i.e only one transfer at a time) is called as a single bus structure. A system is cal led asmultiple bus structure if it contains multiple buses.

11. What is a compiler?

A system software program called a compiler translates the high -level language program into a suitable machine languageprogram containing instructions such as the Add and Load instructions.

12. What is System Software? Give an example?

It is a collection of programs that are executed as needed to perform functions such as

yReceiving and interpreting user commands

y Entering and editing application programs and storing them as files in secondary storagedevices. Ex: Assembler, Linker, Compiler etc

13.What is Application Software? Give an example?

Application programs are usually written in a high -level programming language, in which the programmer specifies

mathematical or text-processing operations. These operations are described in a format that is independent of the particularcomputer used to


3/67

execute the program.

Ex: C, C++, JAVA

14. What is text editor?

It is used for entering and editing application programs . The user of this program interactively executes command that allow

statements of a source program entered at a keyboard to be accumulated in a file.

15. Discuss about OS as system software?

OS is a large program,or actually a collection of routines,t hat is used to control the sharing of and interaction among variouscomputer units as they execute application programs.The OS routines perform the tasks required to assign computerresources to individual application programs.

16. What is multiprogrraming or multitasking?

The operating system manages the concurrent execution of several application programs to make the best possible uses ofcomputer resources.this pattern of concurrent execution is called multiprogrraming or multitasking.

17.What is elapsed time of computer system?

The total time to execute the total program is called elapsed time.it is affected by the speed of the processor,the disk and theprinter.

18. What is processor time of a program?

The periods during which the processor is a ctive is called processor time of a programIt depends on the hardware involved inthe execution of individual machine instructions.

19. Define clock rate?

The clock rate is given by,

R=1/P,where P is the length of one clock cycle.

20. Write down the basic performance equation?

T=N*S/R


4/67

T=processor time

N=no of instructions

S=no of steps

R=clock rate

21.What is pipelining?

The overlapping of execution of successive instructions is called pipelining.

22. What is byte addressable memory?

The assignment of successive addresses to successive byte locations in the memory is called byte addressable memory.

23. What is big endian and little endian format?

The name big endian is used when lower byte addresses are used for the more significiant of the word. The name littleendian is used for the less significiant bytes of the word.

24. What is a branch instruction?

Branch instruction is a type of instruction which loads a new value into the program counter.

25. What is branch target?

As a result of branch instructions , the processor fetches and executes the instruction at a new address called branch target ,instead of the instruction at the location that follows the branch instruction in sequential address order.

26.What are condition code flags?

The processor keep track of information about the results of various operations for use by subsequent conditional branch

instructions. This is accomplished by recording the required information in individual bits, often called conditi on code flags.

27.Define addressing mode.

The different ways in which the location of an operand is specified in an instruction are referred to as addressing modes.


5/67

28.Define various addressing modes.

The various addressing modes are

1.Absolute addressing mode

2.Register addressing mode

3.Indirect addressing mode

4.Index addressing mode

5.Immediate addressing mode

6.Relative addressing mode

7.Autoincrement addressing mode

8.Autodecrement addressing mode

29. What is a pointer?

The register or memory location that contains the address of an operand is called a pointer.

30.What is index register?

In index mode the effective address of the operand is generated by adding a constant value to the contents of a register. Theregister used may be either a special register or may be any one of a set of general purpose registers in the processor. This

register is referred to as an index register.

31.What is assembly language?

A complete set of symbolic names and rules for the use of machines constitute a pr ogramming language, generally referredto as an assembly language.

32.What is assembler directive?

SUM EQU 200

Assembler directives are not instructions that will be executed .It simply informs the assembler that the name SUM shouldbe replaced by the value 200 wherever it appears in the program, such statements are called as assembler directives.

33.What is loader ?

Loader is a system software which contains a set of utility programs. It will load the object program to the memory.


6/67

34.Define device interface.

The buffer registers DATAIN and DATAOUT and the status flags SIN and SOUT are part of circuitry commonly known as

a device interface.

35. What are the basic functional units of a computer?

Input ,memory,arithmetic and logic unit,output and con trol units are the basic functional units of a computer

36. Define Response time and Throughput.

Response time is the time between the start and the completion of the event. Also referred to as execution time orlatency.Throughput is the total amount of work done in a given amount of time

37. Suppose that we are considering an enhancement to the processor of a server system used for web serving.The

new CPU is 10 times faster on computation in the web serving application than the original processor. Assu ming thatthe original CPU is busy with computation 40% of the time and is waiting for I/O 60% of the time. What is the

overall speedup gained by incorporating the enhancement?

Fractionenhanced = 0.4

Speedupenhanced = 10

Speedupoverall = 1/(0.6+0.4/10) =1/0.64 = 1.56

38. Explain the different types of locality.

Temporal locality, states that recently accessed items are likely to be accessed in the near future.Spatial locality, says th atitems whose addresses are near one another tend to be referenced cl ose together in time.

PART B

1.Explain the various addressing modes.

y Register modey Absolute modey Immediate modey Indirect modey Indexed modey Relative modey Auto increment modey Auto Decrement mode

2. Discuss the following:


7/67

(i) Basic operational concepts of a computer.

y Instructionsy Operational details of a processory Registersy Operating steps

(ii) Basic instruction types.

y Zero address instructiony One address instructiony Two address instructiony Three address instruction

3.Discuss in detail the various measures of performance of a computer

y Processor clocky Pipelining and super scalar operationy Clock ratey Instruction sety Compiler

4. Explain briefly about the stack and Queue organization.

y Explanationy Programs

5.Discuss the following:

(i)Instruction execution & straight-line sequencing.

y Execution stepsy Diagram

(ii) Branching.

y Explanationy Diagram

6. Explain in detail the data transfer between the memory & I/O unit.

y Program controlled I/Oy Flags (SIN, SOUT)y Buffers (DATAIN, DATAOUT)y Codingy Diagram


8/67

7.Explain the various functional units of a computer

y Input unity Output Unity ALUy CUy MU

8. Explain the software performance of a computer.

y Explanation

9. Explain the different ways of Bus Structures.

y Input/output devicesy Portsy Networking.

39. How will you compute the SPEC rating?

SPEC stands for system performance Evaluation Corporation

Running time on the reference computer

SPEC rating= _________________________________

Running time on the computer under test

40. When do data hazards arise?

Data hazards arise when an instruction depends on the results of a previous instruction in a way that is expressed by theoverlapping of instructions in the pipeline.

16 Marks

Explain the various addressing modes.

Register mode

Absolute mode

Immediate mode

Indirect mode

Indexed mode

Relative mode


9/67

Auto increment mode

Auto Decrement mode

2. Discuss the following:

(i) Basic operational concepts of a computer.

Instructions

Operational details of a processor

Registers

Operating steps

(ii) Basic instruction types.

Z

ero address instruction

One address instruction

Two address instruction

Three address instruction

3.Discuss in detail the various measures of performance of a computer

Processor clock

Pipelining and super scalar operation

Clock rate

Instruction set

Compiler

4. Explain briefly about the stack and Queue organization.

Explanation

Programs

5.Discuss the following:

(i)Instruction execution & straight -line sequencing.


10/67

Execution steps

Diagram

(ii) Branching.

Explanation

Diagram

6.Explain the various functional units of a computer

Input unit

Output Unit

ALU

CU

MU

7. Explain the software performance of a computer.

Explanation

8.Explain in detail the principle of Carry look ahead adder?

Generate function

Propagate function

4-bit carry look-ahead adder

9. Explain the sequential circuit binary multiplier and give an example for it.

Explanation

Diagram


11/67

10. Explain Booth algorithm for signed -operand multiplication.

Algorithm

Explanation with example

11. Explain the design of fast adders with neat diagrams.

Diagram

Explanation

Read more: CS2253 - COMPUTER ARCHITECTURE - Anna University Engineering Question Bank4

Uhttp://www.questionbank4u.com/index.php?action=view&listid=57&subject=20&semester=9#ixzz1BrBzgd51

Under Creative Commons License: Attribution

Enter to win a free tech book 101 Free Tech Books

UNIT II

PART-A

ARITHMETIC UNIT

1.Give the symbol of a full adder circuit for a single stage addition

2.Give the representation for n bit ripple carry adder

3. Write down the Booths algorithm

Multiplier Version of Multiplicand selected by bit

i

Bit i Bit i-1

0 0 0 x M


12/67

0 1 +1 x M

1 0 -1 x M

1 1 0 x M

4.What are the 2 ways to detect overflow in an n-bit adder?

Overflow can occur when the signs of two operands are the same. Overflow occurs when the carry bits Cn and Cn -1 are

different.

5.What is the delay encountered for Cn-1, Sn-1 and Cn in the FA for a single stage

Cn-1 2(n-1)

Sn-1 2(n-1)+1

Cn 2n

6.What is the delay encountered for all the sum bits in n-bit binary addition/subtraction logic unit?

The gate delays with and without overflow logic are 2n+2 and 2n respectively

7.Write down the basic generate and propagate functions for stage i

Gi = XiYi, Pi=Xi xor with Yi

8.Write down the general expression for Ci+1 using first level generate and propagate function

Ci+1 = Gi+PiGi-1+PiPi-1Gi-2++PiPi-1P1G0+PiPi-1P0G0


13/67

9.What are the two approaches to reduce delay in adders

y Fastest electronic technology in implementing the ripple carry logic designy Augmented logic gate network

10.What is the delay encountered in the path in an n x n array multiplier

The delay encountered in the path in an n x n array multiplier is 6(n-1)-1

11.What is skipping over of ones in Booth decoding?

The Transformation 011 110= +1000 10 is called skipping over ones.In his case multiplier has its ones grouped intoa few contiguous blocks.

12.What are the two attractive features of Booth algorithm

y It handles both positive and negative multipliers uniformlyy It achieves some efficiency in the number of additions required when the multiplier has a few large blocks of ones

13. Give an example for the worst c ase of Booth algorithm

The worst case is shown as below

0 1 0 1 0 1 0 1 0

+1-1+1-1+1-1+1-1+1

In the worst case each bit of the multiplier selects the summands. This results in more number of summands.

14. What are the two techniques for speeding up the multiplication operation?

y Bit Pair recodingy CSA


14/67

15. How bit pair recoding of multiplier speeds up the multiplication process?

It guarantees that the maximum number of summands that must be added is n/2 for nbit operands.

16. How CSA speeds up multiplication?

It reduces the time needed to add the summands. Instead of letting the carries ripple along the rows, they can be saved and

introduced into the next row, at the correct waited position.

17. Write down the levels of C SA steps needed to reduce k summands to two vectors in CSA

The number of levels can be shown by 1.7log2k-1.7

18.What is the advantage of non restoring over restoring division?

Non restoring division avoids the need for restoring the contents of register after

an successful subtraction.

19. Write down the steps for restoring division and non-restoring division Non-Restoring:

Step1: Do the following n times

1.If the sign of A is 0, shift A and Q left one bit position and subtract M from A otherwise shift A and Q left and add M to A.

2.Now if the sign of A is 0, set Q0 to 1; otherwise set Q0 to 0

Step 2: If the sign of A is 1, add M to A

Restoring:

y Shift A and Q left one binary positiony Subtract M from Ay If the sign of A is one , set Q0 to 0, add M back to A otherwise set Q0 to 1

20.What is the need for adding binary 8 value to the true exponential in floating point numbers?

This solves the problem of negative exponent.Due to this the magnitude of the

numbers can be compared.The excess-x representation for exponents enables efficient

comparison of the relative sizes of the two floating point numbers.

21.Briefly explain the floating point representation with an example?


15/67

The floating point representation has 3 fields

1.sign bit

2.significiant bits

3.exponent

For example consider 1.11101100110 x 10^5,

Mantissa=11101100110

Sign=0

Exponent=5

22.What are the 2 IEEE standards for floating point numbers?

1.single

2.double

23.What is overflow, underflow case in single precision(sp)?

Underflow-In SP it means that the normalized representation requires an exponent

less than -126.

Overflow- In SP it means that the normalized representation requires an exponent

greater than +127.

24.What are the exceptions encounted for FP operation?

The exceptions encounted for FP operation are overflow,underflow,/0,inexact and invalid values.

25.What is guard bits?

Guard bits are extra bits which are produced during the intermediate steps to yield maximum accuracy in the final results.

26.What are the ways to truncate guard bits?

1.Chopping

2.Von Neumann rounding

3.Rounding procedure


16/67

PART-B

1.Explain in detail the principle of Carry look ahead adder?

y Generate functiony Propagate functiony 4-bit carry look-ahead adder

2. Explain the sequential circuit binary multiplier and give an example for it.


3. Mention the rules for floating point addition and subtraction and explain how they are implemented?

y Rulesy Diagramy Explanation

4. Multiply the following pair of signed 2s complement number using Bit pair recoding of the multipliers.

A = 010111

B = 101100

5.Perform division on the following 5-bit unsigned integer using Restoring and NonRestoring division:

10101 / 00101

6.Expalin 4X4 array multiplier. What is the delay in this case?

yo

Explanation Diagram


17/67

7. Explain the various types of Adders.

y Half Addero Truth Tableo Explanationo

Full Adder

Truth Table Explanation

8. Explain the various multiple bit Adders

y Carry look-ahead addersy Ripple carry addery Look ahead carry unit

9. Explain the Floating-point arithmetic operations.

y Additiony Multiplication

10. Explain Booth algorithm for signed-operand multiplication.

y Algorithmy Explanation with example

11. Explain the design of fast adders with neat diagrams.

y Diagramy Explanation

2 Marks

Explain MDR and MAR.

The data and address lines of the external memory bus connected to the internal processor bus via the memory data register,MDR, and the memory address register, MAR, respectively. Register MDR has two inputs and two outputs. Dat a may beloaded into MDR either from the memory bus or from the internal processor bus. The data stored in MDR may be placed oneither bus. The input of MAR is connected to the internal bus, and its output is connected to the external bus.

2) Name two special purpose registers.


18/67

Index register

Stack pointer

3) Define datapath.

The registers, the ALU, and the interconnecting bus are collectively referred to as the datapath.

4) Describe the two control signals used for register transfer.

For each register, two control signals are used to place the contents of that register on the bus or to load data on the bus intothe register. The input and output of register Ri are connected to the bus via switches controlled by the signals Riin andRiout, respectively. When Riin is set to 1, the data on the bus are loaded into Ri. Similarly, when Riout is set to 1, the

contents of register Ri are placed on the bus. While Riout is equal to 0, the bus can be used for transferring data from othe rregisters.

5) Define processor clock.

Processor clock is defined as the time periods in which all operations and data transfers with in the processor take place.

6) What is known as multiphase clocking?

When edge-triggered flip flops are not used, two or more clock signals may be needed to guarantee proper transfer of data.

This is known as multiphase clocking.

7) Define MFC.

To accommodate the variability in response time, the processor waits until it receives an indication that the requested readoperation has been completed. The control signal used for this purpose is known as Memory -Function-Completed (MFC).

8) What is WMFC.

WMFC is the control signal that causes the processors control circuitry to wait for the arrival of the MFC signal.

9) Define register file.

All general purpose registers are combined into a single block called the register file.

10) What is mean by branch instruction.


19/67

A branch instruction is an instruction which replaces the contents of the PC with the branch target address. This address isusually obtained by adding an offset X, which is given in the branch instruction, to the updated value of the PC. The locationfollowing a branch instruction is called a branch delay slot.

11) What are the two approaches used for generating the control si gnals in proper sequence?

Hardwired control

Microprogrammed control

12) What are the factors determine the control signals?

1.Contents of the control step counter

2.Contents of the instruction register

3.Contents of the condition code flags

4.External input signals, such as MFC and interrupt requests

13) Explain hardwired control.

The control hardwire can be viewed as a state machine that changes from one state to another in every clock cycle,

depending on the contents of the instruction register, t he condition codes, and the external inputs. The outputs of the statemachine are the control signals. The sequence of operations carried out by this machine is determined by the wiring of the

logic elements, hence the name hardwired.

14) What are the features of the hardwired control.

A controller that uses this approach can operate at high speed. It has little flexibility and the complexity of the instructi on setit can implement is limited.

15) What is microprogrammed control?

Microprogrammed control is a scheme in which control signals are generated by a program similar to machine language

programs.

16) What is control word?

A control word is a word whose individual bits represent the various control signals.

17) Define microroutine and microinstruction.


20/67

A sequence of control words corresponding to the control sequence of a machine instruction constitutes the microroutine forthat instruction, and the individual control words in this microroutine are referred to as microinstructions.

18) What is control store?

The microroutines for all instructions in the instruction set of a computer are stored in a special memory called the controlstore.

19) What is the drawback of assigning one bit position to each control signal?

Assigning individual bits to each control signal results in long microinstructions because the number of required signals isusually large. Moreover, only a few bits are set to 1in any given microinstruction, which means the available bit space is

poorly used.

20) Name some register output control signals.

Pcout, MDRout, Zout, Offsetout, R0out, R1out, R2out, R3out, and TEMPout

21) What is vertical organization and horizontal organization?

Highly encoded schemes that use compact codes to specify only a small number of contr ol functions in eachmicroinstruction are referred to as a vertical organization. On the other hand, the minimally encoded scheme in which many

resources can be controlled with a single microinstruction is called a horizontal organization.

22) Compare vertical organization and horizontal organization.

Vertical organization Horizontal organization

1. Highly encoded schemes

2. Specify only a small number of control signals.

3. Operating speed is high. Minimally encoded schemes

Many resources can be controlled.


21/67

Operating speed is low.

23) Explain bit-O-Ring technique.

The micro program shows that branches are not always made to a single branch address. This is a direct consequence of

combining simple micro routines by sharing common parts. C onsider a point in the microprogram sequencing. At this point,it is necessary to choose between actions required by direct and indirect addressing modes. If the indirect mode is specifiedin the instruction, then the microinstruction in the location 170 i s performed to fetch the operand from the memory. If the

direct mode is specified, this fetch must be bypassed by branching immediately to location 171. The most efficient way tobypass microinstruction 170 is to have the preceding branch microinstructions specify the address 170 and then use an ORgate to change the least significant bit of this address to 1if the direct addressing mode is involved. This is known as the bit-Oring technique for modifying branch addresses.

24) Define emulation.

Given a computer with a certain instruction set, it is possible to define additional machine instructions and implement themwith extra micro routines. Emulation allows us to replace obsolete equipment with more up to date machines. If the

replacement computer fully emulates the original one, then no software changes have to be made to run existing programs.

Thus, emulation facilitates transitions to new computer systems with minimal disruption.

25) What is the drawback of microprogrammed control?

It leads to a slower operating speed because of the time it takes to fetch microinstructions from the control store.

16 Marks

1.Give the basic organization of a Microprogrammed control unit. Draw a flowchart of a micro routine for the instruction

Add Src, Rdst.

Diagram for basic organization

Explanation

Flowchart for Add Src, Rdst

2.Draw the organization of a single -bus processor and give the control sequences for fetching a word from memory, storing aword in memory, executing a complete instruction and unconditio nal and conditional branch.

Diagram

Control Sequences

3.Explain the basic organization of a Hardwired control unit. Mention its advantages and disadvantages.

Diagram for basic organization

Explanation


22/67

Advantages

Disadvantages


Uhttp://www.questionbank4u.com/index.php?action=view&listid=58&subject=20&semester=9#ixzz1BrCEkF1q



UNIT III

PART-A

1) Explain MDR and MAR.

The data and address lines of the external memory bus connected to the internal processor bus via the memory dataregister, MDR, and the memory address register, MAR, respectively. Register MDR has two inputs and two outputs. Datamay be loaded into MDR either from the memory bus or from the internal processor bus. The data stored in MDR may b e

placed on either bus. The input of MAR is connected to the internal bus, and its output is connected to the external bus.

2) Name two special purpose registers.

y Index registery Stack pointer

3) Define datapath.

The registers, the ALU, and the interconnecting bus are collectively referred to as the datapath.

4) Describe the two control signals used for register transfer.

For each register, two control signals are used to place the contents of that register on the bus or to load data on thebus into the register. The input and output of register Ri are connected to the bus via switches controlled by the signals Ri in

and Riout, respectively. When Riin is set to 1, the data on the bus are loaded into Ri. Similarly, when Riout is se t to 1, thecontents of register Ri are placed on the bus. While Riout is equal to 0, the bus can be used for transferring data from othe rregisters.

5) Define processor clock.


23/67

Processor clock is defined as the time periods in which all opera tions and data transfers with in the processor takeplace.

6) What is known as multiphase clocking?

When edge-triggered flip flops are not used, two or more clock signals may be needed to guarantee proper transfer ofdata. This is known as multiphase clocking.

7) Define MFC.

To accommodate the variability in response time, the processor waits until it receives an indication that the requestedread operation has been completed. The control signal used for this purpose is known as Memory-Function-Completed

(MFC).

8) What is WMFC.

WMFC is the control signal that causes the processors control circuitry to wait for the arrival of the MFC signal.

9) Define register file.

All general purpose registers are combined into a single block called the register file.

10) What is mean by branch instruction.

A branch instruction is an instruction which replaces the contents of the PC with the branch target address. Thisaddress is usually obtained by addin g an offset X, which is given in the branch instruction, to the updated value of the PC.

The location following a branch instruction is called a branch delay slot.

11) What are the two approaches used for generating the control signals in proper sequence ?

y Hardwired controly Microprogrammed control

12) What are the factors determine the control signals?

1.Contents of the control step counter

2.Contents of the instruction register

3.Contents of the condition code flags

4.External input signals, such as MFC and interrupt requests


24/67

13) Explain hardwired control.

The control hardwire can be viewed as a state machine that changes from one state to another in every clock cycle,

depending on the contents of the instruction register, the condition codes, and the external inputs. The outputs of the statemachine are the control signals. The sequence of operations carried out by this machine is determined by the wiring of thelogic elements, hence the name hardwired.

14) What are the features of the hardwired control.

A controller that uses this approach can operate at high speed. It has little flexibility and the complexity of the

instruction set it can implement is limited.

15) What is microprogrammed control?

Microprogrammed control is a scheme in which control signals are generated by a program similar to machine

language programs.

16) What is control word?

A control word is a word whose individual bits repre sent the various control signals.

17) Define microroutine and microinstruction.

A sequence of control words corresponding to the control sequence of a machine instruction constitutes themicroroutine for that instruction, and the individual c ontrol words in this microroutine are referred to as microinstructions.

18) What is control store?

The microroutines for all instructions in the instruction set of a computer are stored in a special memory called the

control store.

19) What is the drawback of assigning one bit position to each control signal?

Assigning individual bits to each control signal results in long microinstructions because the number of required

signals is usually large. Moreover, only a few bits are set to 1in any given microinstruction, which means the available bitspace is poorly used.

20) Name some register output control signals.

Pcout, MDRout, Zout, Offsetout, R0out, R1out, R2out, R3out, and TEMPout


25/67

21) What is vertical organization and horizontal organization?

Highly encoded schemes that use compact codes to specify only a small number of control functions in each

microinstruction are referred to as a vertical organization. On the other hand, the minimally encoded scheme in which manyresources can be controlled with a single microinstruction is called a horizontal organization.

22) Compare vertical organization and horizontal organization.

Vertical organization

Horizontal organization

1. Highly encoded schemes

2. Specify only a small number of control signals.

3. Operating speed is high.

Minimally encoded schemes

Many resources can be controlled.

Operating speed is low.

23) Explain bit-O-Ring technique.

The micro program shows that branches are not always made to a single branch address. This is a direct consequenceof combining simple micro routines by sharing common parts. Consider a point in the microprogram sequencing. At this

point, it is necessary to choose between actions required by direct and indirect addressing modes. If the indirect mode isspecified in the instruction, then the microinstruction in the location 170 is performed to fetch the operand from the memory .If the direct mode is specified, this fetch must be bypassed by branching immediately to location 171. The most efficient

way to bypass microinstruction 170 is to have the preceding branch microinstructions specify the address 170 and then usean OR gate to change the least significant bit of this address to 1if the direct addre ssing mode is involved. This is known asthe bit-Oring technique for modifying branch addresses.

24) Define emulation.

Given a computer with a certain instruction set, it is possible to define additional machine instructions and implement

them with extra micro routines. Emulation allows us to replace obsolete equipment with more up to date machines. If thereplacement computer fully emulates the original one, then no software changes have to be made to run existing programs.

Thus, emulation facilitates transitions to new computer systems with minimal disruption.

25) What is the drawback of microprogrammed control?

It leads to a slower operating speed because of the time it takes to fetch microinstructions from the control store.

26) Define pipelining.

Pipelining is an effective way of organizing concurrent activity in a computer system. The processor executes theprogram by fetching and executing instructions, one after the other.


26/67


27/67

33) What is said to be side effect?

When a location other than one explicitly named in an instruction as a destination operand is affected, the instruction

is said to have a side effect.

34) What is dispatch unit?

A separate unit which we call the dispatch unit, takes instructions from the front of the queue and sends them to theexecution unit. The dispatch unit also performs the decoding function.

35) What is branch folding

The instruction fetch unit has executed the branch instruction concurrently with the execution of other instructions.

This technique is referred to as branch folding.

36) What is delayed branching?

A technique called delayed branching can minimize the penalty incurred as a result of conditional branchinstructions. The idea is simple. The instructions in the delay slots are always fetched. Therefore, we would like to arrange

for them to be fully executed whether or not the branc h is taken. The objective is to be able to place useful instructions inthese slots. If no useful instructions can be placed in the delay slots, these slots must be filled with NOP instructions.

37) What are condition codes?

In many processors, the condition code flags are stored in the processor status register. They are either set or clearedby many instructions, so that they can be tested by subsequent conditional branch instructions to change the flow of program

execution.

38) Define speculative execution.

Speculative execution means that instructions are executed before the processor is certain that they are in the correctexecution sequence. Hence, care must be taken that no processor registers or memory locations are update d until it isconfirmed that these instructions should indeed be executed. If the branch decision indicates otherwise, the instructions and

all their associated data in the execution units must be purged , and the correct instructions fetched and executed.

39) What is called static and dynamic branch prediction?

The branch prediction decision is always the same every time a given instruction is executed. Any approach that has

this characteristic is called static branch prediction. Another appr oach in which the prediction decision may changedepending on execution history is called dynamic branch prediction.

40) What are superscalar processors?


28/67


29/67

y Advantagesy Disadvantages

4.Explain the various types of hazards in pipelining?

y Instruction hazardy Data hazardy Structural hazardy Control hazard

5. Write notes on super scalar operation?


6. Explain the multiple bus organization?


7. Explain the techniques used to overcome the various hazards.

y Structural hazardy Duplicating resourcesy Stalling

y Data hazardso Stallingo Duplicating

y Control hazard.y Predicted taken branch schemey Predicted untaken branch schemey Flush or freeze techniquey Delayed branch scheme.

8.Explain the classification of data hazards in pipelining?


30/67

y RAW - Read After Write (also known as True Data Dependency)y WAW - Write After Write (also known as Output Dependency)y WAR - Write After Read (also known as Anti Data Dependency)

9.Explain the Tomasulos approach.

This technique allows execution of instruction to proceed in the presence of hazards.Tomasulos approach

allows renaming of registers dynamically. It buffers operands of instructions waiting to iss ue, fetch them as soon as they areavailable.

y Structure of Tomasulos system.y Instruction statusy Register result statusy Reservation station status

10.Describe about scoreboarding concept.

Scoreboarding is hardware mechanisms that maintain an execution rate of one instruction per cycle by executing aninstruction as soon as its operands are made available and no hazard condition prevent it.

y Overview of scoreboarding techniquey Instruction statusy Register result statusy Functional unit statusy Limitations of scoreboardingy RAW hazards cannot be eliminated

It depends on number, types and speed of the functional units.

2 Marks

1) Define pipelining.

Pipelining is an effective way of organizing concurrent activity in a computer system. The processor executes the programby fetching and executing instructions, one after the other.

2) Name the four steps in pipelining.

Fetch: read the instruction from the memory.

Decode: decode the instruction and fetch the source operand.

Execute: perform the operation specified by the instruction.

Write: store the result in the destination location.

3) What is the use of cache memory?


31/67

The use of cache memories solves the memory access problem. In particular, when a cache is included on the same chip asthe processor, access time to the cache is usually the same as the time needed to perform other basic operations inside the

processor. This makes it possible to divide instruction fetching and processing into steps that are more or less equal induration. Each of these steps is performed by a different pipeline stages, and the clock period is chosen to correspond to thelongest one.

4) What is data hazard?

Any condition that causes the pipeline to stall is called a hazard. A data hazard is any condition in which ei ther the source orthe destination operands of an instruction are not available at the time expected in the pipeline. As a result some operationhas to be delayed, and the pipeline stalls.

5) What are instruction hazards?

The pipeline may also be stalled because of a delay in the availability of an instruction. For example, this may be a result of

a miss in the cache, requiring the instruction to e fetched from the main memory. Such hazards are often called controlhazards or instruction hazards.

6) What are called stalls?

An alternative representation of the operation of a pipeline in the case of a cache miss gives the function performed by eachpipeline stage in each clock cycle. The periods in which the decode unit, execute unit, and the write unit ar e idle are calledstalls. They are also referred to as bubbles in the pipeline.

7) What is structural hazard?

Structural hazard is the situation when two instructions require the use of a given hardware resource at the same time. The

most common case in which this hazard may arise is in access to memory.

8) What is said to be side effect?

When a location other than one explicitly named in an instruction as a destination operand is affected, the instruction is sa idto have a side effect.

9) What is dispatch unit?

A separate unit which we call the dispatch unit, takes instructions from the front of the queue and sends them to theexecution unit. The dispatch unit also performs the decoding function.

10) What is branch folding

The instruction fetch unit has executed the branch instruction concurrently with the execution of other instructions. Thistechnique is referred to as branch folding.


32/67

11) What is delayed branching?

A technique called delayed branching can minimize the penalty incurred as a res ult of conditional branch instructions. The

idea is simple. The instructions in the delay slots are always fetched. Therefore, we would like to arrange for them to be fu llyexecuted whether or not the branch is taken. The objective is to be able to place u seful instructions in these slots. If no useful

instructions can be placed in the delay slots, these slots must be filled with NOP instructions.

12) What are condition codes?

In many processors, the condition code flags are stored in the processor status register. They are either set or cleared by

many instructions, so that they can be tested by subsequent conditional branch instructions to change the flow of programexecution.

13) Define speculative execution.

Speculative execution means that instructi ons are executed before the processor is certain that they are in the correctexecution sequence. Hence, care must be taken that no processor registers or memory locations are updated until it isconfirmed that these instructions should indeed be executed. If the branch decision indicates otherwise, the instructions and

all their associated data in the execution units must be purged , and the correct instructions fetched and executed.

14) What is called static and dynamic branch prediction?

The branch prediction decision is always the same every time a given instruction is executed. Any approach that has this

characteristic is called static branch prediction. Another approach in which the prediction decision may change depending onexecution history is called dynamic branch prediction.

15) What are superscalar processors?

Several instructions start execution in the same clock cycle, and the processor is said to use multiple issue. Such processor s

are capable of achieving an instruction execution throu ghput of more than one instruction per cycle. They are known assuperscalar processors.

16) What is imprecise and precise exception?

Situation in which one or more of the succeeding instructions have been executed to completion is called impreciseexception. Situation in which all subsequent instructions that may have been partially executed are discarded. This is called a

precise exception.

17) What is commitment unit?


33/67

When out-of-order execution is allowed, a special control unit is needed to guarantee in-order commitment. This is called thecommitment unit. It uses a queue called the reorder buffer to determine which instruction should be committed next.Instructions are entered in the queue strictly in program order as they are dispatched for execution.

18) What is a deadlock

A deadlock is a situation that can arise when two units, A and B, use a shared resource. Suppose that unit B cannot completeits task until unit A completes its task. At the same time, unit B has been assigned a resourc e that unit A needs. If this

happens, neither unit can complete its task. Unit A is waiting for the resource it needs, which is being held by unit b. at t hesame time, unit B is waiting for unit A to finish before it canrelease that resource.


Uhttp://www.questionbank4u.com/index.php?action=view&listid=59&subject=20&semester=9#ixzz1BrCPMaY9



UNIT IV

PART-A

MEMORY SYSTEM

1. What is the maximum size of the memory that can be used in a 16 -bit computer and 32 bit computer?

The maximum size of the memory that can be used in a 16 -bit computer is 216=64Kmemory locations.

The maximum size of the memory that can be used in a 32 -bit computer is

232 =4G memory locations.

2. Define memory access time?

The time required to access one word is called the memory access time. Or it is the time that elapses between the

initiation of an operation and the completion of that operation.

3. Define memory cycle time?

It is the minimum time delay required between the initiation of two successive memory operations. Eg. The timebetween two successive read operations.


34/67

4. When is a memory unit called as RAM?

A memory unit is called as RAM if any location can be accessed for a read or write operation in some fixed amount

of time that is independent of the locations address.

5. What is MMU?

MMU is the Memory Management Unit. It is a special memory control circuit used for implementing the map ping ofthe virtual address space onto the physical memory.

6. Define memory cell?

A memory cell is capable of storing one bit of information. It is usually organized in the form of an array.

7. What is a word line?

In a memory cell, all the cells of a row are connected to a common line called as word line.

8. Define static memories?

Memories that consists of circuits capable of retaining their state as long as power

is applied is called Static memories.

9.What are the Characteristics of semiconductor RAM memories?

y They are available in a wide range of speeds.y Their cycle time range from 100ns to less than 10ns.y They replaced the expensive magnetic core memories.y They are used for implementing memories.

10.Why SRAMs are said to be volatile?

Because their contents are lost when power is interrupted. So SRAMs are said to be volatile.

11.What are the Characteristics of SRAMs?

y SRAMs are fast.y They are volatile.y They are of high cost.y Less density.


35/67

12.What are the Characteristics of DRAMs?

y Low cost.y High density.y Refresh circuitry is needed.

13.Define Refresh Circuit?

It is a circuit which ensures that the contents of a DRAM are maintained when each row of cells are accesse dperiodically.

14.Define Memory Latency?

It is used to refer to the amount of time it takes to transfer a word of data to or from the memory.

15.what are asynchronous DRAMs?

In asynchronous DRAMs, the timing of the memory devic e is controlled asynchronously. A specialised memory

controller circuit provides the necessary control signals RAS and CAS that govern the timing.The processor must take intoaccount the delay in the response of the memory. such memories are asynchronous D RAMs .

16.what are synchronous DRAMs?

Synchronous DRAMs are those whose operation is directly synchronized with a clock signal.

17.Define Bandwidth?

When transferring blocks of data, it is of interest to know how much time is needed to transfer an entire block. sinceblocks can be variable in size it is useful to define a performance measure in terms of number of bits or bytes that can betransferred in one second. This measure is often referred to as the memory bandwidth.

18. What is double data rate SDRAMs?

Double data rates SDRAMs are those which can transfer data on both edges of the clock and their bandwidth is

essentially doubled for long burst transfers.

19.What is motherboard?

Mother Board is a main system printed circuit board which contains the processor. It will occupy an unacceptablylarge amount of space on the board.

20.What are SIMMs and DIMMs?


36/67

SIMMs are Single In-line Memory Modules. DIMMs are Dual In -line Memory Modules. Such modules are anassembly of several memory chips on a separate small board that plugs vertically into a single socket on the motherboard.

21.What is memory Controller?

A memory controller is a circuit which is interposed between the processor and the dynamic memory. It is used forperforming multiplexing of address bits.It provides RAS -CAS timing. It also sends R/W and CS signals to the memory.When used with DRAM chips , which do not have self refreshing capability , the memory contr oller has to

provide all the information needed to control the refreshing process.

22. Differentiate static RAM and dynamic RAM?

Static RAM Dynamic RAM

They are fast They are slow

They are very expensive They are less expensive

They retain their state indefinitely They do not retain their state indefinitelyThey require several transistors They require less no transistors.

Low density High density

23. What is Ram Bus technology?

The key feature of Ram bus technology is a fast signaling method used to transfer information between chips. Insteadof using signals that have voltage levels of either 0 or V supply to represent the logic values, the signals consist of muchsmaller voltage swings around a reference voltage, vref. Small voltage swings make it possible to have short transition times,which allows for a high speed of transmission.

24.What are RIMMs?

RDRAM chips can be assembled in to larger modules called RIMMs. It can hold upto 16 RDRAMs.

25. What are RDRAMs?

RDRAMs are Rambus DRAMs. Rambus requires specially designed memory chips. These chips use cell arraysbased on the standard DRAM technology. Multiple banks of cell arrays are used to access more than one word at atime.

Circuitry needed to interface to the Rambus channel is included on the chip. Such chips are known as RDRAMs.

26.What are the special features of Direct RDRAMs?

y It is a two channel Rambus..y It has 18 data lines intended to transfer two bytes of data at a time.y There are no separate address lines.


37/67

27. Define ROM?

It is a non-volatile memory. It involves only reading of stored data.

28.What are the features of PROM?

y They are programmed directly by the user.y Fastery Less expensivey More flexible.

29.Why EPROM chips are mounted in packages that have transparent window?

Since the erasure requires dissipating the charges trapped in the transistors of memory cells. This can be done by

exposing the chip to UV light .

30.What are the disadvantages of EPROM?

The chip must be physically removed from the circuit for reprogramming and its entire contents are erased by theultraviolet light.

31.What are the advantages and disadvantages of using EEPROM?

The advantages are that EEPROMs do not have to be removed for erasure.Also it is possible to erase the cell contentsselectively. The only disadvantage is that different voltages are needed for erasing, writing and reading the stored data.

32.What is cache memory?

It is a small, fast memory that is inserted between the larger, slower main memory and the processor. It reduces thememory access time.

33. Differentiate flash devices and EEPROM devices.

Flash devicesEEPROM devices

It is possible to read the contents

of a single cell, but it is only possible to write an entire block of cells.

It is possible to read and write thecontents of a single cell.

Greater density which leads to higher capacity.

Relatively lower density


38/67

Lower cost per bit. Relatively more cost.

Consumes less power in their operation and makes it more attractive for use inportable equipments that is battery driven.

Consumes more power.

34.Define flash memory?

It is an approach similar to EEPROM technology. A flash cell is based on a single transistor controlled by trappedcharge just like an EEPROM cell.

35. What is locality of reference?

Analysis of programs shows that many instructions in localized areas of the program are executed repeatedly duringsome time period., and the remainder of the program is accessed relatively infrequently. This is referred to as locality ofreference. This property leads to the effectiveness of cache mechanism.

36. What are the two aspects of locality of reference?. Define them.

Two aspects of locality of reference are temporal aspect and spatial aspect. Temporal aspect is that a recently

executed instruction is likely to be executed again very

soon. The spatial aspect is that instru ctions in close proximity to a recently executed instruction are also to be executed soon.

37. Define cache line.

Cache block is used to refer to a set of contiguous address locations of some size. Cache block is also referred to as

cache line.

38.What are the two ways in which the system using cache can proceed for a write

operation?

Write through protocol technique.

Write-back or copy back protocol technique.

39. What is write through protocol?


39/67

For a write operation using write through protocol during write hit: the cache location and the main memory locationare updated simultaneously. For a write miss: For a write miss, the information is written directly to the main memory.

40.When does a readmiss occur?

When the addressed word in a read operation is not in the cache, a read miss

occur.

41. What is write-back or copy back protocol?

For a write operation using this protocol during write hit: the technique is to update only the cache location and tomark it as updated with an associated flag bit, often called the dirty or modified bit. The main memory location of the word

is updated later, when the block containing this marked word is to be removed from the cache to make room for a new block.For a write miss: the block containing the addressed word is first brought into the cache, and then the desired word in thecache is overwritten with the new information.

42.What is load-through or early restart?

When a read miss occurs for a system with cache the required word may be sent to the processor as soon as it is readfrom the main memory instead of loading in to the cache. This approach is called load through or early restart and it reducesthe processors waiting period.

43.What are the mapping technique?

y Direct mappingy Associative mappingy Set Associative mapping

44.What is a hit?

A successful access to data in cache memory is called hit.

45.Define hit rate?

The number of hits stated as a fraction of all attempted access .

46.What are the two ways of constructing a larger module to mount flash chips on a small card?

y Flash cardsy Flash drivers.


40/67

47.Describe the memory hierarchy?

48.Define miss rate?

It is the number of misses stated as a fraction of attempted accesses.

49.Define miss penalty?

The extra time needed to bring the desired information into the cache.

50.Define access time for magnetic disks?

The sum of seek time and rotational delay is called as acce ss time for disks. Seek time is the time required to movethe read/write head to the proper track. Rotational delay or latency is the amount of time that elapses after the head ispositioned over the correct track until the starting position of the address ed sector passes under the read/write head.

51.What is phase encoding or Manchestor encoding?

It is one encoding technique for combining clocking information with data. It is a scheme in which changes in

magnetization occur for each data bit. It s disadvantage is poor bit-storage density.

52.What is the formula for calculating the average access time experienced by the processor?

tave=hc +(1-h)M

Where

h =Hit rate

M=miss penalty

C=Time to access information in the cache.

53. What is the formula for calculating the average access time experienced by the processor in a system with twolevels of caches?

tave =h1c1(1-h1)h2c2+(1-h1)(1-h2)M

where


41/67

h1=hit rate in L1 cache

h2=hit rate in L2 cache

C1=Time to access information in the L1 cache.

C2=Time to access information in the L2 cache.

54.What are prefetch instructions?

Prefetch Instructions are those instructions which can be inserted into a program either by the programmer or by thecompiler.

55.Define system space?

Management routines are part of the operating system of the computer.It is convenient to assemble the OS routinesinto a virtual address space.

56.Define user space?

The system space is separated from virtual address space in which the user application programs reside. The letter

space is called user space.

57.What are pages?

All programs and data are composed of fixed length units called pages.each consists of blocks of words that occupies

contiguous locations in main memory.

58.What is replacement algorithm?

When the cache is full and a memory word that is not in the cache is referenced, the cache control hardware mustdecide which block should be removed to create space for the new block that contains the reference word .The collection ofrules for making this decision constitutes the replacement algorithm.

59.What is dirty or modified bit?

The cache location is updated with an associated flag bit called dirty bit.

60.What is write miss?

During the write operation if the addressed word is not in cache then said to be write miss.


42/67

61.What is associative research?

The cost of an associative cache is higher than the cost of a direct mapped cache because of the need to search all 128

tag patterns to determine whether a given block is in the cache. A search of this kind is called an associative search.

62.What is virtual memory?

Techniques that automatically move program and datablocks into the physical main memory when they are requiredfor execution are called as virtual memory.

63.What is virtual address?

The binary address that the processor used for either instruction or data called as virtual address.

64.What is virtual page number?

Each virtual address generated by the processor whether it is for an instruction fetchis interpreted as a virtual page.

65.What is page frame?

An area in the main memory that can hold one page is called as page frame.

66.What is Winchester technology?

The disk and the read/write heads are placed in a sealed air -filtered enclosure called Winchester technology.

67.What is a disk drive?

The electromechanical mechanism that spins the disk and moves the read/write heads called disk drive.

68.What is disk controller?

The electronic circuitry that controls the operation of the system called as disk controller.

69.What is main memory address?

The address of the first main memory location of the block of words involved in the transfer is called as mainmemory address.


43/67

70.What is word count?

The number of words in the block to be transferred.

71.What is Error checking?

It computes the error correcting code (ECC)value for the data read from a given sector and compares it with the

corresponding ECC value read from the disk.

72.What is booting?

When the power is turned on the OS has to be loaded into the main memory which takes place as part of a processcalled booting.To initiate booting a tiny part of main memory is implemented as a nonvolatile ROM.

73.What are the two states of processor?

y Supervisor statey User state.

74.What is lockup-free?

A cache that can support multiple outstanding misses is called lockup -free.

75.Draw the static RAM cell?

PART-B

1. Write notes on semiconductor RAM memories.

y Internal organization of memory chipsy Static memoriesy Asynchronous DRAMsy Synchronous DRAMs


44/67

y Structure Of Larger Memoriesy Memory System Considerationsy Rambus Memory

2. Write notes on various types of ROMs.

y ROMy PROMy EPROMy EEPROMy Flash Memory

3. What are the various types of cache mapping mechanisms? Explain in detail.

y Direct mappingy Associative mappingy Set Associative mapping

4. Write notes on secondary storage devices.

y Magnetic hard disksy Floppy disksy Optical disksy DVDy Magnetic tape systems

5. Write notes on Virtual memories.

y Address Translationy Diagramy Explanation

6. What are the various techniques used to improve the performance of cache. Explain it.

y Reducing the miss ratey Reducing the miss penaltyy Reducing the miss rate or miss penalty using parallelismy Reducing the time to hit in a cache

7. Explain with neat diagram the internal organization of bit cells in a memory chip.

Hints: Memory cells are usually organized in the form of an array, in which each cell is capable of storing one bit ofinformation. Each row consists a memory word, and all cells of a row are connected to a common line referred to as wordline, which is driven by he address decoder on the chip.


45/67

8. Discuss the virtual memory management technique in detail

Hints: The data is to be stored in physical memory locations that have addresses different from those specified by the

program. The memory control circuitry translates the address specified by the program into an address that can be used toaccess the physical memory.

9. What is memory interleaving? Explain with neat diagram.

Hints: The main memory of a computer is structure as a collection of physically separate modules each with its own address

buffer register and data buffer register, memory access operations may proceed in more tha n one module at the same time.Thus the aggregate rate of transmission of words to and from the main memory system can be increased.

10.Write brief notes on Optical Disks

y CD Technologyy CD-ROMy CD-Recordablesy CD-Rewritablesy DVD Technologyy DVD-RAM

11. Explain in detail Magnetic Hard Disks

y Organization And Accessing Of Data On A Disky Access Timey Typical Disksy Data Buffer/Cachey Disk Controllery Software And Operating System Implicationsy Floppy Disksy Raid Disk Arraysy Commodity Disk Considerations

12. Write notes on Performance Considerations


46/67

y Interleavingy Hit Rate And Miss Penaltyy Caches On Processor Chipy Other Enhancements

16 Marks

1. Write notes on semiconductor RAM memories.

Internal organization of memory chips

Static memories

Asynchronous DRAMs

Synchronous DRAMs

Structure Of Larger Memories

Memory System Considerations

Rambus Memory

2. Write notes on various types of ROMs.

ROM

PROM

EPROM

EEPROM

Flash Memory

3. What are the various types of cache mapping mechanisms? Explain in detail.

Direct mapping

Associative mapping

Set Associative mapping

4. Write notes on secondary storage devices.

Magnetic hard disks

Floppy disks


47/67


48/67

Hints: The main memory of a computer is structure as a collection of physically separate modules each with its own address

buffer register and data buffer register, memory access operations may proceed in more than one module at the same time.Thus the aggregate rate of transmission of words to and from the main memory system can be increased.

10.Write brief notes on Optical Disks

CD Technology

CD-ROM

CD-Recordables

CD-Rewritables

DVD Technology

DVD-RAM

11. Explain in detail Magnetic Hard Disks

Organization And Accessing Of Data On A Disk

Access Time

Typical Disks

Data Buffer/Cache

Disk Controller

Software And Operating System Implications

Floppy Disks

Raid Disk Arrays

Commodity Disk Considerations


49/67

12. Write notes on Performance Considerations

Interleaving

Hit Rate And Miss Penalty

Caches On Processor Chip

Other Enhancement


Uhttp://www.questionbank4u.com/index.php?action=view&listid=60&subject=20&semester=9#ixzz1BrCe7aOO



I/O ORGANIZATION

1.What are called memory-mapped I/O devices?

When I/O devices and the memory share the same address space the arrangement is called memory -mapped I/O devices.

2.What constitutes the devices interface circuit?

The address decoder, the data and the status registers, and the control circuitry required to coordinate I/O transfers

constitute the devices interface circuit.

3.What are the two important mechanisms for implementing I/O operations?

There are two commonly used mechanisms for implementing I/O operations. They are interrupts and direct memoryaccess.

4.What are known as interrupts?

In the case of interrupts, the synchronization is achi eved by having the I/O device send a special signal over the buswhenever it is ready for a data transfer operation.

5.What do you mean by direct memory access?

Direct memory access is a technique used for high speed I/O devices. It involves having the device interface transferdata directly to or from the memory.


50/67

6.What do you mean by an interrupt- request line?

The bus control line is also known as an interrupt -request line.

7.What do you mean by an interrupt acknowledge signal?

The processor must inform the device that its request has been recognized so that it may remove its interrupt -request

signal. This may be accomplished by an interrupt acknowledge signal.

8.What is a subroutine?

A subroutine performs a function required by the program from which it is called.

9.What is interrupt latency?

Saving registers also increases the delay between the time an interrupt request is received and the start of executionof the interrupt-service routine. This delay is called interrupt latency.

10.What is known as real-time processing?

The concept of interrupts is used in operating systems and in many control applications where processing of certain

routines must be accurately timed rel ative to external events .The latter type of application is referred to as real -timeprocessing.

11.What is known as a edge triggered line?

The processor has a special interrupt-request line for which the interrupt handling circuit responds o nly to the leadingedge of a signal .such a line is called a edge -triggered line.

12.What is known as an interrupt vector?

The location pointed to by the interrupting device is used to store the starting address of the interrupt -service routine.The processor reads this address ,called the interrupt vector.

13.What is known as a debugger?

System software usually includes a program called a debugger, which helps the programmer find errors in a program.

14.What is an exception?

The term exception is often used to refer to any event that causes an interruption.


51/67

15.What are known as privileged instructions?

To protect the operating system of a computer from being corrupted by user programs, certain instructions can be

executed only while the processor is in the supervisor mode. These are called privileged instructions.

16.What is known as multitasking?

Multitasking is a mode of operation in which a processor executes several user progra ms at the same time.

17.What is known as time slicing?

A common OS technique that makes multitasking possible is known as time slicing.

18.What is a process?

A program, together with any information that describes its current state of execution, is regarded by the OS as anentity called a process.

19.What is a device driver?

A self contained module that encapsulates all software pertaining to a particular device is known as a device driver.

20.What is data abort?

Data abort arises from an error in reading or writing data.

21.What is known as prefetch abort?

Prefetch abort arises from an error when prefetching instructions from the memory.

22.What are banked registers?

The registers that replace user mode registers are called banked registers.

23.What is known as direct memory access?

A special control unit may be provided to allow transfer of a block of data directly between an external device andthe main memory, without continuous intervention by the processor. This approach is called direct memory access, or DMA.


52/67

24.What is known as a DMA controller?

DMA transfers are performed by a control circuit that is part of the I/O device interface. This circuit is known as

DMA controller.

25.What is known as cycle stealing?

The processor originates most memory access cycles, the DMA controller can be said to steal memory cycles from

the processor. Hence ,this interweaving technique is usu ally called cycle stealing.

26.What is known as block/burst mode?

The DMA controller may be given exclusive access to the main memory to transfer a block of data without interrupt.This is known as block/burst mode.

27.What is called a bus master?

The device that is allowed to initiate data transfers on the bus at any given time is called the bus master.

28.What is known as distributed arbitration?

Distributed arbitration means that all devices waiting to use the bu s have equal responsibility in carrying out thearbitration process, without using a central arbiter

29.What is a strobe?

Strobe captures the values of the data given instant and store them into a buffer.

30.What is meant by handshake?

Handshake is used between the master and the slave for controlling data transfers on the bus.

31. What is known as full handshake?

A change of state in one signal is followed by a change in the other signal. This is known as a full handshake.

32.What is a bitrate?

The speed of transmission is known as a bit rate.


53/67

33.What is a initiator?

A master is called an initiator in PCI technology.

34.What is called a target?

The addressed device that responds to read and write commands is called a target.

35.What is a transaction?

A complete transfer operation on the bus involving an address and a burst of data ,is called a transaction.

36.What are sectors?

Data are stored on a disk in blocks called sectors.

37.What are known as asynchronous events?

The event of pressing a key is not synchronized to any other event in a computer system.the data generated by thekeyboard are called asynchronous.

38.What are known as isochronous events?

The sampling process yields a continuous stream of digitized samples that arrive at regular intervals,synchronized

with the sampling clock.

39.What is known as plug- and- play?

The plug-and play feature means that a new device ,such as an additional speaker, can be connected at any timewhile the system is operating.

40.What is called a hub?

Each node of the tree has a device called a hub which acts as an intermediate control point between the host and theI/O devices.


54/67

41.What is a root hub?

At the root of a tree, a root hub connects the entire tree to the host computer.

42.What are called functions in USB terminology?

The leaves of the tree are the I/O devices being served which are called functions of the USB terminology.

43.What are called pipes?

The purpose of the USB software is to provide bi-directional communication links between application software andI/O devices. These links are called pipes.

44.What are called endpoints?

Locations in the device to or from which data transfer can take place ,such as status, control, and data registers arecalled endpoints.

45.What is a frame?

Devices that generate or receive isochronous data require a time reference to control the sampling process. To

provide this reference, transmission over the USB is divided into frames of equal length.

46.What is the length of a frame?

A frame is 1 ms long for low-and full-speed data.

PART-B

1. Explain the various methods available to handle multiple devices using interrupts?

yVectored interrupt

y Interrupt nestingy Simultaneous requests

2. Write notes on interrupts in operating system?

y Explanation


55/67

3. Explain DMA and the different types of bus arbitration mechanisms.

y Diagramy Explanationy Centralized arbitrationy Decentralized arbitration

4. Explain the accessing of I/O devices.

y Computers use a single bus arrangement.

y It consists of 3 lines to carry address, data and control signals. Each I/O device is assigned a set of uniqueaddresses.

y When the I/O devices and the memory share the same address space, the arrangement is called memory -mappedI/O.

y With memory-mapped I/O, any machine that can access memory can be used to transfer data.

y The address decoder enables the device to recognize its address when it appears on the address lines.

y The data reg. holds the data to be transferred to the processor.

y The status register contains information relevant to t he operation of I/O device

y The address decoder, the data and status reg. and the control circuitry required to coordinate I/O transfersconstitute the devices interface circuits.

5.Explain Synchronous and Asynchronous bus.

y Synchronous buso In a Synchronous bus all devices derive timing information from a common clock line.o Each interval constitutes a bus cycle,during which one data transfer can take place.o Explain with an example.


56/67

o The clock speed must be chosen such that it accommodates the longe st delays on the bus and the slowestinterface.

y Asynchronous buso An alternative scheme for controlling data transfers on the bus is based on the use of a handshake

between the processor and the device being addressed.o The common clock is eliminated.o The clock line is replaced by two timing control lines, which we refer to as Ready and Accept.o Explain with an example.

6.Explain the Interface circuits.

y The I/O interface consists of the circuitry required to transfer data between the computer bus and an I/ O device.y On one side of the interface we have the bus signals for the address, data and control.y On the other side we have a data path with its associated controls, which enables transfer of data between the

interface and the I/O device. This side is devi ce-independent.

y It can be classified as (i) parallel interface and (ii) serial interface.y Parallel Interfacey

Serial Interface

yo A parallel interface transfers data in the form of one or more bytes simultaneously to or from the device.o Explain an example with suitable diagrams.

yo A Serial interface is used to connect the processor to I/O devices that require transmission of data one bit

at a time.

o The key feature of a serial interface is a circuit capable of communicating in bit -serial fashion on thedevice side and in bit-parallel fashion on the bus side.

y Transformation between parallel and serial formats is achieved with shift registers that have parallel accesscapability.

yo The most common use of the serial interface is in connecting the computer to devices that are a

considerable distance away.o The speed of transmission gives the bit rate.

7.Explain the Peripheral Component Interconnect (PCI) Bus.

y The PCI bus is a good example of a system bus that grew out of the need for Standardization.y Devices connected to the PCI bus appear to the processor as if they were connected directly to the processor bus.y They are assigned addresses in the memory address space of the processor.y The PCI was developed as a low cost bus that is truly processor independent.y An important feature that PCI pioneered is a plug -and-play capability for connecting I/O devices.y At any time, one device is the bus master.y A master is called an initiator in PCI terminology. This is either a processor or a DMA controller.y The addressed devicey That responds to read and write commands is called a target.y A complete transfer operation on the bus,involving an address and a burst of data is called a transaction.y Individual word transfers within a transaction are called phases.y When an I/O device is connected to a computer several actions are needed to configure both the device and the

software that communicates with it.


57/67

y Explain an example.

8.Explain the SCSI Bus.

y SCSI stands for Small Computer System Interface. y It refers to a std. bus defined by the ANSI. y The SCSI bus standard has undergone many revisions, and its data transfer capability has increased very rapidly.y A SCSI bus may have 8 data lines, in which case it is called a narrow bus and transfers data only one bit at a tim e.yy A wide SCSI bus has 16 data lines and transfers 16 bits at a time. y Devices connected to the SCSI bus are not part of the address space of the processor in the same way as devices

connected to the processor bus.

y Data are stored on a disk in blocks called sectors, where each sector may contain several hundred bytes. y A controller connected to a SCSI bus is one of two types -an initiator or a target. y An initiator has the ability to select a particular target. y The initiator establishes a logical conne ction with the intended target.y Explain the sequence of events that take place when the processor sends a command to the SCSI controller.

9.Explain Universal Serial Bus (USB).

y The USB supports two speeds of operation, called low-speed(1.5 megabits/s) and full-speed(12 megabits/s).y The most recent revision of the bus specification introduced a third operation, called high -speed (480 megabits/s).y The USB is quickly gaining acceptance in the market place.y To add new ports, a user must open the computer b ox to gain access to the internal expansion bus and install a new

interface card.

y The kinds of devices that may be connected to a computer cover a wide range of functionality.y The sampling process yields a continuous stream of digitized samples that arrive at regular intervals, synchronized

with the sampling clock. Such a data stream is called isochronous.

y A signal must be sampled quickly enough to track its highest -frequency components.y An important requirement in dealing with sampled voice or music is to maintain precise timing in the sampling

and replay processes.

y A high degree of jitter is unacceptable. 2 Marks

1.What are called memory-mapped I/O devices?

When I/O devices and the memory share the same address space the arrangement is called memory -mapped I/O devices.

2.What constitutes the devices interface circuit?

The address decoder, the data and the status registers, and the control circuitry required to coordinate I/O transfers consti tute

the devices interface circuit.


58/67

3.What are the two important mechanisms for implementing I/O operations?

There are two commonly used mechanisms for implementing I/O operations. They are interrupts and direct memory access.

4.What are known as interrupts?

In the case of interrupts, the synchronization is achieved by having the I/O device send a special signal over the bus

whenever it is ready for a data transfer operation.

5.What do you mean by direct memory access?

Direct memory access is a technique used for high speed I/O devices. It involves having t he device interface transfer datadirectly to or from the memory.

6.What do you mean by an interrupt - request line?

The bus control line is also known as an interrupt -request line.

7.What do you mean by an interrupt acknowledge signal?

The processor must inform the device that its request has been recognized so that it may remove its interrupt -request signal.

This may be accomplished by an interrupt acknowledge signal.

8.What is a subroutine?

A subroutine performs a function required by the program fr om which it is called.

9.What is interrupt latency?

Saving registers also increases the delay between the time an interrupt request is received and the start of execution of theinterrupt-service routine. This delay is called interrupt latency.

10.What is known as real-time processing?

The concept of interrupts is used in operating systems and in many control applications where processing of certain routines

must be accurately timed relative to external events .The latter type of application is referred to as real-time processing.

11.What is known as a edge triggered line?

The processor has a special interrupt -request line for which the interrupt handling circuit responds only to the leading edge

of a signal .such a line is called a edge-triggered line.


59/67

12.What is known as an interrupt vector?

The location pointed to by the interrupting device is used to store the starting address of the interrupt -service routine .The

processor reads this address ,called the interrupt vector.

13.What is known as a debugger?

System software usually includes a program called a debugger, which helps the programmer find errors in a program.

14.What is an exception?

The term exception is often used to refer to any event that causes an interruption.

15.What are known as privileged instructions?

To protect the operating system of a computer from being corrupted by user programs, certain instructions can be executedonly while the processor is in the supervisor mode. These are called privileged instructions.

16.What is known as multitasking?

Multitasking is a mode of operation in which a processor executes several user programs at the same time.

17.What is known as time slicing?

A common OS technique that makes multitasking possible is known as time slicing .

18.What is a process?

A program, together with any information that describes its current state of execution, is regarded by the OS as an entity

called a process.

19.What is a device driver?


60/67

A self contained module that encapsulates all software pertaining to a particular device is known as a device driver.

20.What is data abort?

Data abort arises from an error in reading or writing data.

21.What is known as prefetch abort?

Prefetch abort arises from an error when prefetching instructions from the memory.

22.What are banked registers?

The registers that replace user mode registers are called banked registers.

23.What is known as direct memory access?

A special control unit may be provided to allow transfer of a block of data directly between an external device and the mainmemory, without continuous intervention by the processor. This approach is called direct memory access, or DMA.

24.What is known as a DMA controller?

DMA transfers are performed by a control circuit that is part of the I/O device interface. This circuit is known as DMA

controller.

25.What is known as cycle stealing?

The processor originates most memory access cycles, the DMA controller can be said to steal memory cycles from theprocessor. Hence ,this interweavi ng technique is usually called cycle stealing.

26.What is known as block/burst mode?

The DMA controller may be given exclusive access to the main memory to transfer a block of data without interrupt. This isknown as block/burst mode.

27.What is called a bus master?


61/67

The device that is allowed to initiate data transfers on the bus at any given time is called the bus master.

28.What is known as distributed arbitration?

Distributed arbitration means that all devices wai

Date post:	09-Apr-2018
Category:	Documents
Upload:	revathy-jayabaskar
View:	216 times
Download:	0 times

ca question bank

Documents