81. Assuming all numbers are in 2's complement representation, which of the following numbers is divisible by 11111011?
a. 11100111
b. 11100100
c. 11010111
d. 11011011
Answer: (a).11100111

82. For a pipelined CPU with a single ALU, consider the following situations

1. The j + 1-st instruction uses the result of the j-th instruction
as an operand
2. The execution of a conditional jump instruction
3. The j-th and j + 1-st instructions require the ALU at the same

Which of the above can cause a hazard ?
a. 1 and 2 only
b. 2 and 3 only
c. 3 only
d. All of above
Answer: (d).All of above

83. The literal count of a boolean expression is the sum of the number of times each literal appears in the expression. For example, the literal count of (xy + xz') is 4. What are the minimum possible literal counts of the product-of-sum and sum-of-product representations respectively of the function given by the following Karnaugh map ? Here, X denotes "don't care".
a. (11, 9)
b. (9, 13)
c. (9, 10)
d. (11, 11)
Answer: (c).(9, 10)

84. Consider the ALU shown below. If the operands are in 2's complement representation, which of the following operations can be performed by suitably setting the control lines K and C0 only (+ and - denote addition and subtraction respectively) ?
a. A + B, and A - B, but not A + 1
b. A + B, and A + 1, but not A - B
c. A + B, but not A - B, or A + 1
d. A + B, and A - B, and A + 1
Answer: (a).A + B, and A - B, but not A + 1

85. Consider the following circuit composed of XOR gates and non-inverting buffers. The non-inverting buffers have delays d1 = 2 ns and d2 = 4 ns as shown in the figure. Both XOR gates and all wires have zero delay. Assume that all gate inputs, outputs and wires are stable at logic level 0 at time 0. If the following waveform is applied at input A, how many transition(s) (change of logic levels) occur(s) at B during the interval from 0 to 10 ns ?
a. 1
b. 2
c. 3
d. 4
Answer: (d).4

86. Consider the grammar rule E → E1 - E2 for arith­metic expressions. The code generated is targeted to a CPU having a single user register. The sub­traction operation requires the first operand to be in the register. If E1 and E2 do not have any com­mon sub expression, in order to get the shortest possible code
a. E1 should be evaluated first
b. E2 should be evaluated first
c. Evaluation of E1 and E2 should necessarily be interleaved
d. Order of evaluation of E1 and E2 is of no consequence
Answer: (b).E2 should be evaluated first

87. If 73x (in base-x number system) is equal to 54y (in base-y number system), the possible values of x and y are
a. 8, 16
b. 10, 12
c. 9, 13
d. 8, 11
Answer: (d).8, 11

88. Which of the following addressing modes are suitable for program relocation at run time ?

(i) Absolute addressing
(ii) Based addressing
(iii) Relative addressing
(iv) Indirect addressing
a. (i) and (iv)
b. (i) and (ii)
c. (ii) and (iii)
d. (i), (ii) and (iv)
Answer: (c).(ii) and (iii)

89. Consider the partial implementation of a 2-bit counter using T flip-flops following the sequence 0-2-3-1-0, as shown below. To complete the circuit, the input X should be
a. Q2'
b. Q2 + Q1
c. (Q1 ⊕ Q2)'
d. Q1 ⊕ Q2
Answer: (d).Q1 ⊕ Q2

90. The microinstructions stored in the control memory of a processor have a width of 26 bits. Each microinstruction is divided into three fields: a micro-operation field of 13 bits, a next address field (X), and a MUX select field (Y). There are 8 status bits in the inputs of the MUX.
How many bits are there in the X and Y fields, and what is the size of the control memory in number of words?
a. 10, 3, 1024
b. 8, 5, 256
c. 5, 8, 2048
d. 10, 3, 512
Answer: (a).10, 3, 1024