VLSI TEST QUESTIONS AND
ANSWERS
Why do we want both low-k and high-k dielectrics in advanced CMOS? -
ANSWER Low-k: Wire dielectrics should be low capacitance to improve
performance and power
High-k Gate dielectrics should be high capacitance to form a strong conducting
channel
If an SRAM row decoder takes a 4-bit address and generates 16-word lines,
what is the probability that a given word line will switch? - ANSWER Each
time the address changes, one word line will turn on and another will turn off.
This the probability of any one word-line switching in either direction will be
1/16 + 1/16. We usually only look at switches 0->1 for power calculations, so
the relevant answer should be 1/16.
Why is authenticated encryption an important capability in an implantable
medical device? - ANSWER Confidentiality and authentication of medical
data.
An implantable med device has access to very private and important personal
info.
Insurance fraud and identity theft.
If the length of the NMOS transistor decreases, does the high noise margin
NMH increase, decrease or stay the same? Sketch the VTC. - ANSWER
NMOS transistor length decreasing means larger W/L and hench a stronger
pull-down, increased beta N. This means the NMH will increase.
, What is a fabless semiconductor company? Name one. - ANSWER Only
designs and does not manufacture chips.
Apple.
What is a foundry? Name one. - ANSWER A foundry manufactures chips for
other firms.
Global Foundry
Draw a timing diagram that shows how increased clock skew t(skew) can
DECREASE the maximum clock frequency f(max). - ANSWER Clock skew
is one clock signal arriving at two places, but they're now different signals
/ \___/ \___/ \___/
_/ \___/ \___/ \___/
Explain how the estimate of 20pJ/op is applied across a wide range of
computing applications. - ANSWER See the DARPA slide.
The value of 20pJ/op accross varying scales and frequencies, from
supercomputers to implantable medical devices.
Question 10 on final - ANSWER Each stage in the arbiter consists of 2 2-input
multiplexors.
The arbiter is another 2-input multiplexor.
Total is 129 2-input multiplexor.
Area should be in lambda.
What does NoC stand for? - ANSWER Network on Chip
ANSWERS
Why do we want both low-k and high-k dielectrics in advanced CMOS? -
ANSWER Low-k: Wire dielectrics should be low capacitance to improve
performance and power
High-k Gate dielectrics should be high capacitance to form a strong conducting
channel
If an SRAM row decoder takes a 4-bit address and generates 16-word lines,
what is the probability that a given word line will switch? - ANSWER Each
time the address changes, one word line will turn on and another will turn off.
This the probability of any one word-line switching in either direction will be
1/16 + 1/16. We usually only look at switches 0->1 for power calculations, so
the relevant answer should be 1/16.
Why is authenticated encryption an important capability in an implantable
medical device? - ANSWER Confidentiality and authentication of medical
data.
An implantable med device has access to very private and important personal
info.
Insurance fraud and identity theft.
If the length of the NMOS transistor decreases, does the high noise margin
NMH increase, decrease or stay the same? Sketch the VTC. - ANSWER
NMOS transistor length decreasing means larger W/L and hench a stronger
pull-down, increased beta N. This means the NMH will increase.
, What is a fabless semiconductor company? Name one. - ANSWER Only
designs and does not manufacture chips.
Apple.
What is a foundry? Name one. - ANSWER A foundry manufactures chips for
other firms.
Global Foundry
Draw a timing diagram that shows how increased clock skew t(skew) can
DECREASE the maximum clock frequency f(max). - ANSWER Clock skew
is one clock signal arriving at two places, but they're now different signals
/ \___/ \___/ \___/
_/ \___/ \___/ \___/
Explain how the estimate of 20pJ/op is applied across a wide range of
computing applications. - ANSWER See the DARPA slide.
The value of 20pJ/op accross varying scales and frequencies, from
supercomputers to implantable medical devices.
Question 10 on final - ANSWER Each stage in the arbiter consists of 2 2-input
multiplexors.
The arbiter is another 2-input multiplexor.
Total is 129 2-input multiplexor.
Area should be in lambda.
What does NoC stand for? - ANSWER Network on Chip
