Wednesday, 31 August 2016

A Level July, 2013 A4-R4: COMPUTER SYSTEM ARCHITECTURE

A Level July, 2013
A4-R4: COMPUTER SYSTEM ARCHITECTURE


TOTAL TIME: 3 HOURS TOTAL MARKS: 100
(PART ONE – 40; PART TWO – 60)
PART ONE
(Answer all the questions)

1. Each question below gives a multiple choice of answers. Choose the most appropriate one and enter in the “OMR” answer sheet supplied with the question paper, following instructions therein. (1x10)
1.1 Which one among the following 2 Input logic gates can be used to implement any other 2 Input
Logic gates?
A) AND
B) EX-OR
C) OR
D) NOR
1.2 What is the FAN-OUT of any standard TTL Logic Gate?
A) 2
B) 1
C) 10
D) 5

1.3 The 16’s complement or F’s complement of the HEX Number -2AB will be
A) 0FAC
B) FD55
C) FD54
D) EE55
1.4 Which among the following F/Fs is best suited to implement any synchronous counter?
A) J-K F/F.
B) T F/F
C) D F/F
D) S-R F/F
1.5 How many Half Adder Blocks are needed to implement a 1 bit Full Adder?
A) 2
B) 1
C) 3
D) 4

1.6 In order to access an Array element in any assembly language instruction, which among the
following addressing modes happens to be most suitable?
A) Memory Direct.
B) Memory Indirect.
C) Register Indirect.
D) Based Indexed.
1.7 Within any CPU, the special purpose register provided to access the Stack Memory is termed
as
A) Instruction Pointer.
B) Memory Data Register.
C) Stack Pointer.
D) Memory Address Register.
1.8 Multiplication Algorithm as supported by any Hardware Unit is essentially composed of which
essential steps?
A) Left Shift and Subtraction.
B) Right Shift and Subtraction.
C) Left Shift and Addition.
D) Right Shift and Addition.
1.9 For any Peripheral Device like Disk, whose Data Transfer Rate to Memory can be faster than
the rate at which the CPU can handle, which among the following Data Transfer Techniques
happens to be most suitable?
A) Interrupt Driven.
B) Polling.
C) DMA.
D) None of the above.
1.10 Which among the following technologies is employed to build the Main Memory of modern day
Laptops and PCs?
A) Static RAM.
B) Magnetic RAM.
C) Dynamic RAM.
D) Flash Memory.

2. Each statement below is either TRUE or FALSE. Choose the most appropriate one and ENTER in the “OMR” answer sheet supplied with the question paper, following instructions therein. (1x10)

2.1 EX –OR gate is the building block of any Adder.
2.2 Preset Input in a D F/F can be used to set its output to 0 asynchronously.
2.3 In Binary 2’s complement scheme there exists separate representations for +0 and -0.
2.4 Tri-State control is necessary only at the output ports of each & every storage item that is
connected to a shared bus.
2.5 Instruction cycle refers to the time taken by the CPU in fetching any machine coded instruction
completely from the concerned memory.
2.6 Memory Address Register & Memory Data Register together represent the gateway for the CPU
to the external world of memory & peripherals.
2.7 Overflow Flag in any CPU is relevant for unsigned operands only.
2.8 Interrupt driven data transfer is an Asynchronous mode of Data Transfer.
2.9 Cache memory is actually a static RAM.
2.10 Address operand in any 8086 instruction happens to be 20 bit wide.

3. Match words and phrases in column X with the closest related meaning/word(s)/phrase(s) in column Y. Enter your selection in the “OMR” answer sheet supplied with the question paper, following instructions therein. (1x10)

                                X                                                                        Y

3.1 3 Inputs and 8 Outputs Combinational Circuit                      A. -8
3.2 Inverter is another way to call                                               B. A NOT Gate.
3.3 Both Inputs fed with 1 will represent an                               C. 256 number of different machine op
                                                                                                          codes. Unstable state in a
3.4 1000 in 4 bit two’s complement will have a                          D. An OR Gate
Decimal Equivalent
3.5 ALU happens to be                                                                E. A mixture of combinational and
sequential circuit blocks.
3.6 8 bit wide Machine Op Code will lead to                            F. Only Arithmetic Right shifting of the
                                                                                                        Partial Result
3.7 Data Transfer Instruction can possess                                 G. Is speed compatible with CPU
maximum
3.8 In Booth’s multiplication algorithm a stream of                 H. Subtraction of Multiplicand from the
0s or 1s will cause                                                                            partial result.

3.9 In order to transfer Data from a slow device to                    I. 2 Operand Addresses.
CPU
3.10 Cache Memory                                                                    J. Handshaking mechanism must be
there.
                                                                                                     K. S-R F/F.
                                                                                                     L. A purely combinational circuit.
                                                                                                     M. 3 to 8 Decoder

4. Each statement below has a blank space to fit one of the word(s) or phrase(s) in the list below. Enter your choice in the “OMR” answer sheet supplied with the question paper,following instructions therein. (1x10)

A. Storage                                        B. Content                                         C. Instruction
D. Segmented                                   E. Edge                                             F. Data
G. Right                                            H. 1 Giga                                          I. 1 Mega
J. Indirectly                                       K. Asynchronous                              L. Logic ‘1’
M. EX-OR

4.1 In TTL +ve logic 5 Volt is treated as ________.
4.2 For single binary bit comparison ________ gate can be used.
4.3 ________ Triggering is preferred for building D F/Fs.
4.4 No ALU possesses any form of ________ element.
4.5 Cache Memory is usually ________ addressable.
4.6 In a 4 Gbyte memory having 32 bit Word size can actually store ________ distinct 32 bit words.
4.7 In 8086 ________ addressing is used to access any memory element.
4.8 All types of peripheral data transfer employs ________ mode of operation.
4.9 For dividing a binary integer by decimal 8, shift it ________ by 3 bits.
4.10 In the Assembly instruction JUMP TARGET the operand TARGET refers to an ________
address.
A4-R4 Page 5 of 5 July, 2013
PART TWO
(Attempt any FOUR questions)
5.
a) Specify the Truth Table of a 1 bit Binary Full Adder that can be used to ADD single bit binary
numbers x and y as well as a carry input c in to produce the result bit z along with carry output
c out..
b) Use the Truth Table of (a) to implement the Binary Full Adder that ADDs single bit binary
numbers x and y as well as a carry input c in to produce the result bit z along with carry output
c out using 2 Level AND-OR Logic Circuit. Specify ALL design steps.
(8+7)
6. Using J-K F/Fs, specify the Logic structure of the ith stage of an n- bit Universal Register cum
Counter in which the user based on a set of Control Inputs will be able to configure it in one
from among the following mode.
i) Load from External Input.
ii) Shift LEFT the stored bit pattern by 1 bit.
iii) Shift RIGHT the stored bit pattern by 1 bit.
iv) Count UP.
v) Count Down.
You are to specify all the key DESIGN Steps along with relevant premises and assumptions as
well as BLOCK Level Diagram.
(15)
7.
a) Specify the brief steps of the Booth’s algorithm when employed to multiply two 4 bit signed (2’s
complement) binary numbers. A (a3a2a1a0) and B (b3b2b1b0) where a3 and b3 happen to be the
respective signs.
b) Illustrate the actions of that algorithm in a stepwise fashion when it is used to multiply –7
(decimal) with +5 (decimal).
(7+8)
8.
a) Just by consulting the instruction set of any CPU, is it possible to ascertain whether the CPU
possesses a separate I/O space? Justify your answer with examples.
b) During execution of an instruction by the CPU the following requests come simultaneously from
several peripheral devices.
i) DMA request.
ii) Interrupt request.
iii) RDY signal from a slow Input Device.
Clearly specify the actions that the CPU will take. In what order the aforesaid requests will be
served and why?
(3+12)
9. In a computer system, a 2 K byte of RAM module is to be implemented using 128 x 4 bit RAM
chips. The CPU possesses a 20 bit address bus and a data bus of 8 bit width.
a) How many such chips will be needed and there will be how many pins at the minimum on each
chip? Clearly depict ALL calculation. What will be the relevant pin signals? Justify & label the
presence of each of them.
b) Does there exist any mechanism by which the given 2K RAM space can be placed anywhere in
the 20 bit Address space? Discuss in brief about the same.
(12+3)

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