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    VLSI Chap 6 MCQs

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    VLSI Chap 6 MCQs

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    VLSI Example mvqs

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    VLSI Example mvqs

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    4 views8 pages

    VLSI Chap 6 MCQs

    Uploaded by

    Next Step
    VLSI Example mvqs

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
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    Question 1:

    What is the primary reason interconnect plays a major role in modern VLSI system
    performance?
    Options:
    A. Wires have become thicker, reducing resistance.
    B. Transistors switch slower, and wires are wider.
    C. Wire RC delay exceeds gate delay, and capacitive coupling causes crosstalk.
    D. On-chip interconnect inductance is negligible.
    Answer: C. Wire RC delay exceeds gate delay, and capacitive coupling causes crosstalk.

    Question 2:

    What is the aspect ratio of a wire in interconnect geometry?


    Options:
    A. Width to length ratio (w/l).
    B. Thickness to width ratio (t/w).
    C. Spacing to thickness ratio (s/t).
    D. Dielectric height to wire thickness ratio (h/t).
    Answer: B. Thickness to width ratio (t/w).

    Question 3:

    Why did aluminum (Al) wires give way to copper (Cu) in CMOS processes?
    Options:
    A. Copper has a higher resistivity than aluminum.
    B. Copper reduces resistance, improving interconnect performance.
    C. Aluminum cannot handle high temperatures.
    D. Copper is easier to manufacture than aluminum.
    Answer: B. Copper reduces resistance, improving interconnect performance.

    Question 4:

    In interconnect modeling, what does the pipe analogy represent?


    Options:
    A. Resistance relates to the wire’s cross-sectional area.
    B. Inductance is modeled as a trough underneath the pipe.
    C. Capacitance relates to a paddle wheel along the wire.
    D. None of the above.
    Answer: A. Resistance relates to the wire’s cross-sectional area.
    Question 5:

    In the example of resistance calculation, what is the total resistance of a 0.22 µm thick Cu wire
    with a width of 0.125 µm and length of 1 mm?
    Options:
    A. 0.1 Ω.
    B. 0.8 Ω.
    C. 800 Ω.
    D. 8 Ω.
    Answer: C. 800 Ω.

    Let me share the remaining MCQs directly here as well.

    Question 6:

    What is the primary impact of crosstalk in interconnect?


    Options:
    A. Increased resistance of wires.
    B. Noise and delay variations on neighboring wires.
    C. Reduced capacitance of wires.
    D. Improved energy efficiency.
    Answer: B. Noise and delay variations on neighboring wires.

    Question 7:

    What is the purpose of low-k dielectrics in interconnects?


    Options:
    A. Reduce resistance.
    B. Increase inductance.
    C. Reduce capacitance.
    D. Improve mechanical stability.
    Answer: C. Reduce capacitance.

    Question 8:

    What does the L-model represent in interconnect modeling?


    Options:
    A. Lumped resistance and capacitance in a wire.
    B. Distributed resistance and inductance in a wire.
    C. A simplified delay model for long wires.
    D. A poor choice for modeling accurate results.
    Answer: D. A poor choice for modeling accurate results.
    Question 9:

    What is the significance of the Miller Coupling Factor (MCF) in interconnects?


    Options:
    A. Describes how inductance affects delay.
    B. Represents effective capacitance to adjacent wires.
    C. Measures resistance variations in a wire.
    D. Predicts the propagation of noise in power grids.
    Answer: B. Represents effective capacitance to adjacent wires.

    Question 10:

    What factor does the skin effect influence in high-frequency interconnects?


    Options:
    A. Capacitance increases at high frequencies.
    B. Resistance decreases due to current spreading.
    C. Resistance increases as current flows near the conductor surface.
    D. Inductance becomes negligible.
    Answer: C. Resistance increases as current flows near the conductor surface.

    Question 11:

    What is the Elmore delay for a single-segment π-model?


    Options:
    A. RC.
    B. RC/2.
    C. 2RC.
    D. R + C.
    Answer: B. RC/2.

    Question 12:

    What is the typical capacitance of tightly pitched metal lines?


    Options:
    A. 0.1 fF/µm.
    B. 0.2 fF/µm.
    C. 0.5 fF/µm.
    D. 1.0 fF/µm.
    Answer: B. 0.2 fF/µm.

    Question 13:
    What is a common method for reducing interconnect delay in long wires?
    Options:
    A. Using higher-k dielectrics.
    B. Reducing wire spacing.
    C. Adding repeaters along the wire length.
    D. Decreasing wire thickness.
    Answer: C. Adding repeaters along the wire length.

    Question 14:

    What happens to interconnect delay as wire length increases?


    Options:
    A. Delay remains constant.
    B. Delay increases linearly.
    C. Delay grows quadratically.
    D. Delay decreases.
    Answer: C. Delay grows quadratically.

    Question 15:

    What is the effect of increased wire spacing on interconnects?


    Options:
    A. Reduces coupling capacitance and noise.
    B. Increases resistance.
    C. Decreases energy efficiency.
    D. Increases inductance.
    Answer: A. Reduces coupling capacitance and noise.

    Question 16:

    What is the primary purpose of inserting repeaters in a long wire?


    Options:
    A. To reduce the wire's capacitance.
    B. To minimize inductance effects.
    C. To break the delay into linear segments.
    D. To eliminate crosstalk.
    Answer: C. To break the delay into linear segments.

    Question 17:

    What is the primary cause of inductive crosstalk in interconnects?


    Options:
    A. Capacitance between adjacent wires.
    B. Current loops generating magnetic fields.
    C. Resistance variations in wires.
    D. Dielectric breakdown between layers.
    Answer: B. Current loops generating magnetic fields.

    Question 18:

    What is the typical skin depth for a copper wire in CMOS circuits?
    Options:
    A. 10 nm.
    B. 50 nm.
    C. 0.1 µm.
    D. 1 µm.
    Answer: C. 0.1 µm.

    Question 19:

    What is the primary advantage of using low-swing signaling in interconnects?


    Options:
    A. Reduces delay and power consumption.
    B. Eliminates inductive effects.
    C. Simplifies the design of drivers.
    D. Increases the voltage swing of signals.
    Answer: A. Reduces delay and power consumption.

    Question 20:

    Which of the following methods reduces inductive effects in a power grid?


    Options:
    A. Using higher resistance metals.
    B. Increasing the spacing between wires.
    C. Ensuring dense power grids with low SR ratios.
    D. Increasing wire thickness without adding ground planes.
    Answer: C. Ensuring dense power grids with low SR ratios.

    Question 21:

    What happens to interconnect resistance when temperature increases?


    Options:
    A. It decreases exponentially.
    B. It remains constant.
    C. It increases by approximately 0.4% per °C.
    D. It decreases linearly with higher temperatures.
    Answer: C. It increases by approximately 0.4% per °C.

    Question 22:

    What is the effect of shielding wires in interconnects?


    Options:
    A. Increases the delay of critical signals.
    B. Eliminates noise and coupling effects.
    C. Increases the spacing between tracks.
    D. Decreases the mechanical stability of layers.
    Answer: B. Eliminates noise and coupling effects.

    Question 23:

    What is the coupling capacitance ratio for modern wires with a t/w aspect ratio of 2 or more?
    Options:
    A. 1/3 of the total capacitance.
    B. 1/2 of the total capacitance.
    C. 2/3 of the total capacitance.
    D. Negligible compared to total capacitance.
    Answer: C. 2/3 of the total capacitance.

    Question 24:

    What is a key feature of twisted differential signaling?


    Options:
    A. Reduces the area of the power grid.
    B. Cancels noise from inductive and capacitive coupling.
    C. Increases the number of repeaters required.
    D. Simplifies the driver circuit design.
    Answer: B. Cancels noise from inductive and capacitive coupling.

    Question 25:

    What is the energy required per bit per unit length for a repeated wire sized for minimum delay?
    Options:
    A. Equal to the unrepeated wire energy.
    B. About 50% more than the unrepeated wire energy.
    C. About 87% more than the unrepeated wire energy.
    D. Twice the unrepeated wire energy.
    Answer: C. About 87% more than the unrepeated wire energy.

    Question 26:

    What is the delay per unit length of a properly repeated wire expressed in FO4 delay?
    Options:
    A. 0.77 FO4.
    B. 1.67 FO4.
    C. 2.0 FO4.
    D. 3.0 FO4.
    Answer: B. 1.67 FO4.

    Question 27:

    Which parameter determines the propagation delay in the Elmore delay model for distributed
    RC circuits?
    Options:
    A. Wire length.
    B. Capacitance to ground.
    C. Resistance and capacitance distributed along the wire.
    D. Coupling capacitance.
    Answer: C. Resistance and capacitance distributed along the wire.

    Question 28:

    What is the best distance between repeaters in a long wire to minimize delay?
    Options:
    A. Directly proportional to wire resistance.
    B. Inversely proportional to wire capacitance.
    C. Proportional to the square root of wire resistance and capacitance.
    D. Inversely proportional to the driver size.
    Answer: C. Proportional to the square root of wire resistance and capacitance.

    Question 29:

    How does increasing the wire width affect interconnect properties?


    Options:
    A. Reduces resistance but increases capacitance.
    B. Increases resistance and reduces inductance.
    C. Reduces both resistance and capacitance.
    D. Increases coupling noise and inductance.
    Answer: A. Reduces resistance but increases capacitance.

    Question 30:

    Which technique is NOT used to control interconnect crosstalk?


    Options:
    A. Increasing wire spacing.
    B. Adding shielding wires.
    C. Interleaving busses.
    D. Using higher resistance materials.
    Answer: D. Using higher resistance materials.

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