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Roll No. .................................. 
Fifth Semester [B.Tech]  September 2005
Paper Code : ETCS – 305 Subject : Computer Architecture 
Time : 1^{1}/_{2} Hours 
Maximum Marks : 30 
Note : Attempt any 3 questions in all. Q1 is compulsory. Each question carries 10 marks. 
Q1 
( a ) 
How many bits wide memory addresses have to be if the computer had 16 MB of memory? (Use the smallest value possible) 
1 
( b ) 
Derive the correct floating point representation of the decimal numbers +3.5 and 2.1 using the 32 bit IEEE 754 floating point standard.  2  
( c ) 
Consider the following floating points: Mantissa of X = 110011, Exponent of X = 1100111 Mantissa of Y = 000001, Exponent of Y = 1101111 Perform operations X + Y. 
1.5  
( d ) 
Differentiate between Selective 
2  
( e ) 
The following transfer statements specify a memory. Explain the
memory operation in each case i) R2 < M[AR] ii) M[AR] < R3 
1.5  
( f )  Differentiate between Classical method and One Hot method of Control Design.  1.5 
Q2 
( a ) 
Design an arithmetic circuit with one selection input S and two
nbit data inputs A and B. The circuit generates the following four
arithmetic operations:

1 + 4*1 

( b ) 
A digital computer has a common bus system for 12 registers of 9 bits each. The bus is constructed with multiplexers.

Q3 
( a ) 
The system uses a control memory of 1024 words of 32 bits each. The
microinstruction has three fields for microoperations. select a
status bit and Brach address field. The microoperation field has 16
bits.

2+2+1 
( b ) 
The contents of the PC in the basic computer is 3AF (all numbers in
HEX). The contents of AC are 7EC3. The contents of memory at address
3AF are 09AC. The contents of memory at address 9AC is 8B9F. Assume
opcode 001 stands for ADD operation.

0.5 + 0.5 + 4 
Q4 
( a ) 
Write a program to evaluate the arithmetic statement:

5 
( b ) 
A two word instruction is stored in memory at an address designated
by the symbol W. The address field of the instruction (stored at
W+1) is designated by the symbol Y. The operand used during the
execution of the instruction is stored at an address symbolized by
Z. An index register contains the value X. State how Z is calculated
from the other addresses if the addressing mode of the instruction
is: (Give explanation also)

1*5 