VLSI Multiple Choice Questions on “System Considerations”.
1. Clock line drivers has ____________ source of drive.
A. one
B. two
C. three
D. none
Answer: A
Clarification: Clock line drivers have one source of drive. The speed of bipolar drivers is not fully realized with bus lines.
2. Bus structures carry ____________
A. data signals
B. control signals
C. data and control signals
D. in and out signals
Answer: C
Clarification: Bus structures carry both data and control signals. They are generally long and connected to and through a significant number of circuits and subsystems.
3. Bus has _______ different classes.
A. two
B. three
C. four
D. five
Answer: B
Clarification: Bus has three different classes and those are passive, active and precharged.
4. In passive bus, drivers are connected through
A. series switches
B. parallel switches
C. cascade switches
D. wires
Answer: A
Clarification: In passive bus, drivers are connected through series switches. It is a floating rail to which signals may be connected from drivers through series switches.
5. The bus rail in active bus has ________
A. NAND connection
B. AND connection
C. NOR connection
D. OR connection
Answer: C
Clarification: The bus rail in active bus has NOR connection which has a common pull up and ntype pull down transistors.
6. Low L:W ratio results in ____ transistors.
A. smaller
B. bigger
C. size doesnt depend on ratio
D. less effective
Answer: B
Clarification: The size of the transistor can be made large by small L:W ratio and thus it has a low resistance.
7. Features which does not affect bus design are ________
A. cross-talk
B. delay factors
C. non delay factors
D. cross talk and delay factors
Answer: C
Clarification: Cross-talk and delay factors are of significance in bus design. This occurs when many signals on chip is propogated.
8. Which device is frequency dependent?
A. nMOS
B. CMOS
C. BiCMOS
D. pMOS
Answer: B
Clarification: CMOS is frequency dependent where as BiCMOS is not and it exhibits constant value for power dissipation.
9. If the current density exceeds a threshold value then metal atoms moves in
A. direction of the current
B. opposite direction of the current
C. doesnt depend on direction of current
D. direction of the voltage
Answer: A
Clarification: If the current density exceeds a threshold value then metal atoms starts to move in the direction of current.
10. At narrowing or constriction point current density is ________
A. minimum
B. maximum
C. remains low after going to high point
D. becomes high from low
Answer: B
Clarification: At narrowing or constriction point, current density is at its highest. At these points, metal is transported from the constricted regions become even more constricted and eventually may blow like a fuse.
11. During relaxation effect, electron flow occurs in
A. short pulses
B. at steady state level
C. large pulses
D. very large pulses
Answer: A
Clarification: During relaxation effect, electron flow occurs in short pulses rather than at steady state level.
12. Line impedance is given by
A. (L/C.2
B. (C/L)2
C. (L/C.1/2
D. (C/L)1/2
Answer: C
Clarification: The line impedance Zo is given by (L/C.1/2 where L and C are values per unit length of the bus.
13. IR drops brings ______ in noise margin.
A. increase
B. decrease
C. does not affect
D. stabilisation
Answer: B
Clarification: IR drops bring about deterioration in noise margins. Transient voltages induced in either Vdd or Vss rail may lead to noise margin problems.