Multi-Core Computer Architecture | Week 4

Session: JULY-DEC 2023

Course Name: Multi-Core Computer Architecture

Course Links: Click Here

These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q1. Loop unrolling results in
increasing register pressure
decreasing I cache miss
increasing number of control hazards
increasing control dependence

Answer: increasing register pressure

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Q2. In Tomasulo’s algorithm, register renaming is done using
Compiler scheduling
Reservation Station
Reorder Buffer
Common Data Bus

Answer: Reservation Station

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q3. Which one of the following statements is FALSE?
Compiler can achieve instruction level parallelism using strip mining.
A normal in-order multi cycle MIPS pipeline can never achieve an IPC larger than 1.
In a MIPS multi-cycle floating point pipeline that supports operand forwarding, there will be six stalls between a pair of adjacent MUL instructions that has a RAW dependency between them.
WAW and WAR are true data dependencies.

Answer: WAW and WAR are true data dependencies.

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Q4. Register Renaming can solve
WAR and WAW hazards
RAW hazard only
WAR hazard only
RAW, WAR, and WAW hazards

Answer: WAR and WAW hazards

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q5. Which of the following is the best match from Set A to Set B?
Set A Set B
W. Static Scheduling 1. Reorder buffer
X. Operand Forwarding 2. Loop unrolling
Y. Speculative Dynamic Scheduling 3. RSI Update
Z. CDB writing 4. Reservation station
W→3 X→1 Y →4 Z → 2
W→2 X→4 Y→1 Z → 3
W→2 X→4 Y→3 Z → 1
W→3 X→2 Y→1 Z → 4

Answer: W→2 X→4 Y→1 Z → 3

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q6. In a dynamically scheduled processor that supports speculation, if the register status indicator of a register Rx is 0, then
the latest value of Rx can be obtained from the entry #0 in the re-order buffer.
the latest value of Rx will be produced by functional unit #0.
the latest value of Rx can be obtained from the entry #0 in the reservation station.
the latest value of Rx is available in the Register File.

Answer: the latest value of Rx is available in the Register File.

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q7. Consider an ADD instruction with first operand as Rx and second operand as Ry that is to be executed in a dynamically scheduled processor that follows Tomasulo’s algorithm. When the instruction is issued, the seven-tuple entry {Op, Qj, Qk, Vj, Vk, A, Busy} in the reservation station for this instruction is {ADD, 2, 0, 0, 2, A, 1}. Which of the following information is correct about the operands of this ADD instruction?
Rx value is available from output of functional unit #2 and Ry value is available from output of functional unit #0.
Rx value is 2 and Ry value is available from output of functional unit #0.
Rx value is available from output of functional unit #2 and Ry value is 2.
Rx value is 2 and Ry value is 0.

Answer: Rx value is available from output of functional unit #2 and Ry value is 2.

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q8. Suppose, a load and a store access the same address. If in program order the store appears before the load, interchanging them in execution order can create __ hazard.
RAW
WAR
WAW
No

Answer: RAW

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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Q9. Consider an instruction pipeline with an issue width of 1 that uses Tomasulo’s algorithm with one reservation station per functional unit. There is one Integer MUL unit, one Integer DIV unit, and one Integer ADD unit, all connected to a single CDB. The functional units are not pipelined. An instruction waiting for data on CDB can move to its EX stage in the cycle after the CDB broadcast. The instructions are:
I1: ADDI R1, R1, #8
I2: DIV R3, R2, R1
I3: MUL R4, R1, R3
I4: DIV R5, R4, R1
Assume the following information about functional units.
Functional unit type Cycles in EX stage
Integer MUL unit 4
Integer DIV unit 8
Integer ADD unit 1
In which cycle does instruction I3 write to CDB?

Answer: 17

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These are Multi-Core Computer Architecture Nptel Week 4 Answers

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