VLSI Questions and Answers – Multiplier Systems

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This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “Multiplier Systems”.

1. Multipliers are built using
a) binary adders
b) binary subtractors
c) dividers
d) multiplexers
View Answer

Answer: a
Explanation: A multiplier is an electronic circuit used to multiply two bianry numbers. It is built using binary adders that is full adders.
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2. Which method uses reduced number of partial products?
a) baugh-wooley algorithm
b) wallace trees
c) dadda multipliers
d) modified booth encoding
View Answer

Answer: d
Explanation: Multiplication in multipliers is done by obtaining partial products and then summing it up. Modified booth encoding reduces the number of partial products that must be summed.

3. Which method is easier to manipulate accumulator content?
a) left shifting
b) right shifting
c) serial shifting
d) parallel shifting
View Answer

Answer: b
Explanation: It is easier to right shift the contents of accumulator than to left shift. This can be used to eliminate the least significant bits of the product.

4. Which multiplier is very well suited for twos complement numebers?
a) baugh-wooley algorithm
b) wallace trees
c) dadda multipliers
d) modified booth encoding
View Answer

Answer: a
Explanation: Baugh-wooley method is used to design multipliers that are regular in structure and is very well suited for twos complement numbers.
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5. What is the delay required to perform a single operation in pipelined structure?
a) 2n
b) 3n
c) 4n
d) n
View Answer

Answer: b
Explanation: The delay of one operation through the pipeline is 3n that is it takes 3n clock cycles to obtain a product after X and Y are input.

6. Latches choosen are
a) static shift registers
b) any flipflop
c) dynamic shift register
d) multiplexers
View Answer

Answer: c
Explanation: The latches choosen are dynamic shift register as the structure will be continuously clocked.

7. Which method reduces number of cycles of operation?
a) baugh-wooley algorithm
b) wallace trees
c) dadda multipliers
d) modified booth encoding
View Answer

Answer: d
Explanation: Modified booth encoding algorithm avoids many idle cells in a cellular multiplier as well as reduces the number of cycles compared with the serial-parallel multiplier.
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8. The completion time for multiplication time in baugh-wooley method is
a) n
b) 2n
c) 3n
d) 4n
View Answer

Answer: b
Explanation: The completion time for multiplication in Braun or Baugh-wooley is proportional to 2n where as completion time in Wallace tree method is proportional to log(base 2)(n).

9. In which method minimum number of adder cells are used?
a) baugh-wooley algorithm
b) wallace trees
c) dadda multipliers
d) modified booth encoding
View Answer

Answer: c
Explanation: Dadda multipliers are similar to Wallace trees but it has reduced number of adder cells. This is a technique developed from Wallace tree but with an improvement.

10. Which method is suitable for larger operands?
a) baugh-wooley algorithm
b) wallace trees
c) dadda multipliers
d) modified booth encoding
View Answer

Answer: b
Explanation: Wallace tree multipliers should be used for larger operands and where the performance is critical.
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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn