Out-of-Order Execution MCQs – T4Tutorials.com

What is out-of-order execution in CPU architecture?
a) Executing instructions in the order they appear in the program
b) Executing instructions in an order different from the program order
c) Executing only the most recent instructions
d) Ignoring the instruction order entirely
Answer: b) Executing instructions in an order different from the program order

The main advantage of out-of-order execution is:
a) Increased instruction fetch rate
b) Improved CPU pipeline efficiency
c) Reduced memory access latency
d) Enhanced power consumption
Answer: b) Improved CPU pipeline efficiency

Which hardware component is primarily responsible for implementing out-of-order execution?
a) Memory management unit
b) Instruction scheduler
c) Arithmetic Logic Unit
d) Cache controller
Answer: b) Instruction scheduler

What is the purpose of the instruction reordering in out-of-order execution?
a) To reduce instruction latency
b) To improve instruction cache performance
c) To ensure sequential consistency
d) To increase the clock speed
Answer: a) To reduce instruction latency

Which of the following is a common issue in out-of-order execution?
a) Cache coherence
b) Instruction fetch rate
c) Branch prediction
d) Instruction dependency
Answer: d) Instruction dependency

In out-of-order execution, what is the role of the instruction window?
a) To cache instructions for future execution
b) To hold instructions that are waiting to be executed
c) To reorder instructions before execution
d) To manage instruction fetch operations
Answer: b) To hold instructions that are waiting to be executed

Which of the following techniques helps resolve data hazards in out-of-order execution?
a) Branch prediction
b) Register renaming
c) Cache replacement
d) Memory interleaving
Answer: b) Register renaming

What is register renaming used for in out-of-order execution?
a) To increase the number of registers available
b) To eliminate false data dependencies
c) To improve memory access speed
d) To optimize cache usage
Answer: b) To eliminate false data dependencies

The primary challenge of implementing out-of-order execution is:
a) Increased instruction fetch bandwidth
b) Complex instruction scheduling
c) Reduced register file size
d) Simplified pipeline design
Answer: b) Complex instruction scheduling

In out-of-order execution, what is a “scoreboard”?
a) A cache used for instruction storage
b) A mechanism for tracking instruction status and dependencies
c) A unit that handles instruction decoding
d) A method for branch prediction
Answer: b) A mechanism for tracking instruction status and dependencies

Which of the following is NOT a benefit of out-of-order execution?
a) Reduced instruction execution time
b) Increased power consumption
c) Enhanced parallelism
d) Improved pipeline utilization
Answer: b) Increased power consumption

What type of dependency does out-of-order execution aim to resolve?
a) Control dependency
b) Data dependency
c) Structural dependency
d) Timing dependency
Answer: b) Data dependency

What is a “reorder buffer” in out-of-order execution?
a) A cache that stores frequently used instructions
b) A buffer that holds instructions until they can be committed in order
c) A unit that renames registers
d) A mechanism for branch prediction
Answer: b) A buffer that holds instructions until they can be committed in order

Which of the following best describes the role of the instruction scheduler in out-of-order execution?
a) To fetch instructions from memory
b) To execute instructions sequentially
c) To determine the order in which instructions are executed
d) To decode instructions into machine code
Answer: c) To determine the order in which instructions are executed

What is a potential drawback of out-of-order execution?
a) Reduced instruction throughput
b) Increased complexity of CPU design
c) Increased instruction fetch time
d) Simplified instruction scheduling
Answer: b) Increased complexity of CPU design

In out-of-order execution, what is meant by “issue stage”?
a) The stage where instructions are decoded
b) The stage where instructions are sent to the execution units
c) The stage where instructions are committed to the register file
d) The stage where instructions are fetched from memory
Answer: b) The stage where instructions are sent to the execution units

Which technique helps reduce the impact of branch mispredictions in out-of-order execution?
a) Branch prediction
b) Register renaming
c) Out-of-order issue
d) Instruction reordering
Answer: a) Branch prediction

What does the term “instruction window” refer to in out-of-order execution?
a) The number of instructions that can be fetched per cycle
b) The number of instructions held and managed for execution
c) The range of memory addresses used for instruction fetching
d) The time taken for an instruction to be executed
Answer: b) The number of instructions held and managed for execution

How does out-of-order execution affect cache utilization?
a) It improves cache hit rates by predicting future instructions
b) It reduces the need for large caches
c) It can cause increased cache misses due to instruction reordering
d) It eliminates the need for cache coherence
Answer: c) It can cause increased cache misses due to instruction reordering

What is the “commit stage” in out-of-order execution?
a) The stage where instructions are fetched
b) The stage where instructions are decoded
c) The stage where instructions are written back to the register file
d) The stage where instructions are executed
Answer: c) The stage where instructions are written back to the register file

In out-of-order execution, which of the following is used to manage instruction dependencies?
a) Instruction buffer
b) Dependency map
c) Issue queue
d) Reorder buffer
Answer: d) Reorder buffer

What is the primary role of the execution units in out-of-order processors?
a) To decode instructions
b) To schedule instructions
c) To execute instructions as soon as they are ready
d) To fetch instructions from memory
Answer: c) To execute instructions as soon as they are ready

How does out-of-order execution affect instruction-level parallelism (ILP)?
a) It reduces ILP
b) It increases ILP by allowing instructions to execute as soon as dependencies are resolved
c) It has no effect on ILP
d) It decreases the number of instructions that can be executed
Answer: b) It increases ILP by allowing instructions to execute as soon as dependencies are resolved

What is a “data hazard” in the context of out-of-order execution?
a) When an instruction depends on data that has not yet been produced
b) When multiple instructions are executed simultaneously
c) When instructions are fetched out of sequence
d) When instructions are reordered incorrectly
Answer: a) When an instruction depends on data that has not yet been produced

Which component helps in managing the state of instructions in out-of-order execution?
a) Instruction fetch unit
b) Instruction decoder
c) Instruction scheduler
d) Instruction status register
Answer: c) Instruction scheduler

What is “speculative execution” in out-of-order processors?
a) Executing instructions based on predicted paths before the actual path is known
b) Reordering instructions after execution
c) Waiting for all dependencies to be resolved before executing
d) Running instructions in the exact program order
Answer: a) Executing instructions based on predicted paths before the actual path is known

Which of the following is NOT typically used to resolve control hazards in out-of-order execution?
a) Branch prediction
b) Speculative execution
c) Register renaming
d) Instruction buffering
Answer: c) Register renaming

In out-of-order execution, what does “out-of-order issue” refer to?
a) Issuing instructions in the program order
b) Issuing instructions based on availability rather than order
c) Issuing instructions only when all dependencies are resolved
d) Issuing instructions only to the next execution unit
Answer: b) Issuing instructions based on availability rather than order

What role does the “issue queue” play in out-of-order execution?
a) It holds instructions until they can be executed
b) It stores the results of executed instructions
c) It manages memory accesses
d) It schedules the execution of instructions
Answer: a) It holds instructions until they can be executed

Which of the following is a challenge associated with speculative execution?
a) Increased instruction throughput
b) Increased power consumption and complexity
c) Reduced instruction latency
d) Simplified control flow
Answer: b) Increased power consumption and complexity

In out-of-order execution, what is a “commit” operation?
a) Moving instructions from the issue queue to the execution units
b) Writing the results of instructions back to the register file
c) Fetching instructions from memory
d) Decoding instructions into machine code
Answer: b) Writing the results of instructions back to the register file

What does the term “data forwarding” refer to in out-of-order execution?
a) Forwarding instructions to the next execution unit
b) Passing data between instructions without waiting for the previous instruction to complete
c) Moving data from memory to registers
d) Passing data between different stages of the pipeline
Answer: b) Passing data between instructions without waiting for the previous instruction to complete

Which of the following techniques can help reduce the impact of mispredicted branches in out-of-order execution?
a) Increasing the instruction window size
b) Implementing advanced branch prediction algorithms
c) Reducing the number of execution units
d) Decreasing the number of registers
Answer: b) Implementing advanced branch prediction algorithms

How does out-of-order execution improve CPU performance?
a) By increasing clock speed
b) By allowing multiple instructions to execute simultaneously
c) By reducing the number of instructions
d) By simplifying the CPU design
Answer: b) By allowing multiple instructions to execute simultaneously

What is “instruction window size” in out-of-order execution?
a) The number of instructions fetched per cycle
b) The number of instructions that can be held and managed for execution
c) The size of the cache used for instructions
d) The number of execution units available
Answer: b) The number of instructions that can be held and managed for execution

What is the function of “out-of-order commit” in a CPU?
a) To execute instructions in the order they are fetched
b) To commit the results of instructions out of their original order
c) To manage instruction fetch operations
d) To resolve data dependencies
Answer: b) To commit the results of instructions out of their original order

In out-of-order execution, what does “speculative execution” entail?
a) Executing instructions based on predicted paths and rolling back if predictions are incorrect
b) Executing only the most recent instructions
c) Waiting for all dependencies to resolve before executing
d) Executing instructions in the exact program order
Answer: a) Executing instructions based on predicted paths and rolling back if predictions are incorrect

What is a “bypass path” in the context of out-of-order execution?
a) A path that bypasses memory access
b) A path that allows instructions to be executed without waiting for data from previous instructions
c) A path that increases the number of execution units
d) A path that handles branch mispredictions
Answer: b) A path that allows instructions to be executed without waiting for data from previous instructions

Which of the following best describes “out-of-order dispatch”?
a) Dispatching instructions to execution units in the order they are fetched
b) Dispatching instructions to execution units based on availability and readiness
c) Dispatching instructions after all dependencies are resolved
d) Dispatching instructions to memory before execution
Answer: b) Dispatching instructions to execution units based on availability and readiness

What role does the “dependency tracker” play in out-of-order execution?
a) It tracks the status of data and instruction dependencies
b) It tracks the memory addresses of instructions
c) It tracks the cache hit and miss rates
d) It tracks the number of execution units
Answer: a) It tracks the status of data and instruction dependencies

Which of the following is NOT a common challenge in out-of-order execution?
a) Register file pressure
b) Increased complexity
c) Reduced instruction throughput
d) Managing dependencies
Answer: c) Reduced instruction throughput

In the context of out-of-order execution, what does “instruction issue” refer to?
a) The process of fetching instructions from memory
b) The process of sending instructions to the execution units based on their readiness
c) The process of decoding instructions into machine code
d) The process of committing instruction results
Answer: b) The process of sending instructions to the execution units based on their readiness

Which of the following is an effect of increasing the size of the instruction window in out-of-order execution?
a) Decreased instruction throughput
b) Reduced power consumption
c) Increased parallelism and improved performance
d) Increased instruction latency
Answer: c) Increased parallelism and improved performance

In out-of-order execution, what is the role of the “branch predictor”?
a) To predict the outcomes of conditional branches to minimize delays
b) To reorder instructions for optimal execution
c) To manage the instruction window size
d) To decode instructions into machine code
Answer: a) To predict the outcomes of conditional branches to minimize delays

What is “dynamic scheduling” in out-of-order execution?
a) Scheduling instructions statically before execution
b) Scheduling instructions based on their readiness and availability dynamically during execution
c) Scheduling instructions based on the clock speed
d) Scheduling instructions based on program order
Answer: b) Scheduling instructions based on their readiness and availability dynamically during execution

What is a “pipeline stall” in the context of out-of-order execution?
a) A delay in the pipeline caused by instruction dependencies
b) An increase in clock speed
c) A reduction in the number of execution units
d) An increase in the size of the instruction window
Answer: a) A delay in the pipeline caused by instruction dependencies

Which component of an out-of-order CPU is responsible for ensuring that instructions are executed in the correct order?
a) Instruction scheduler
b) Reorder buffer
c) Execution unit
d) Cache controller
Answer: b) Reorder buffer

In out-of-order execution, what is the main purpose of the “instruction issue queue”?
a) To store instructions waiting to be executed
b) To decode instructions into machine code
c) To manage memory accesses
d) To fetch instructions from memory
Answer: a) To store instructions waiting to be executed

How does out-of-order execution help improve CPU utilization?
a) By reducing the need for multiple cores
b) By allowing the CPU to execute instructions that are not dependent on others
c) By simplifying the CPU design
d) By increasing the clock speed
Answer: b) By allowing the CPU to execute instructions that are not dependent on others

Which of the following describes “out-of-order completion” in a CPU?
a) Completing instructions in the exact program order
b) Completing instructions in the order they are executed
c) Completing instructions out of their original order but ensuring correctness
d) Completing instructions before their execution
Answer: c) Completing instructions out of their original order but ensuring correctness

In out-of-order execution, what does “speculative execution” refer to?
a) Executing instructions based on predicted outcomes and rolling back if predictions are incorrect
b) Executing instructions in a fixed order regardless of dependencies
c) Executing only the most recent instructions
d) Executing instructions only when all dependencies are resolved
Answer: a) Executing instructions based on predicted outcomes and rolling back if predictions are incorrect

What is the function of a “scoreboard” in out-of-order execution?
a) To track instruction dependencies and status
b) To manage memory access
c) To fetch instructions from memory
d) To decode instructions
Answer: a) To track instruction dependencies and status

Which of the following helps manage instruction dependencies in out-of-order execution?
a) Instruction cache
b) Data cache
c) Reorder buffer
d) Instruction window
Answer: c) Reorder buffer

How does “dynamic scheduling” differ from “static scheduling”?
a) Dynamic scheduling schedules instructions based on real-time availability, while static scheduling schedules instructions before execution begins
b) Static scheduling schedules instructions based on real-time availability, while dynamic scheduling schedules instructions before execution begins
c) Dynamic scheduling is simpler than static scheduling
d) Dynamic scheduling is used only for memory operations
Answer: a) Dynamic scheduling schedules instructions based on real-time availability, while static scheduling schedules instructions before execution begins

What is the role of the “memory disambiguation” technique in out-of-order execution?
a) To optimize memory access by predicting future accesses
b) To resolve ambiguities in memory access instructions to avoid conflicts
c) To increase memory size
d) To fetch memory instructions in the correct order
Answer: b) To resolve ambiguities in memory access instructions to avoid conflicts

What impact does out-of-order execution have on instruction throughput?
a) It decreases instruction throughput
b) It has no effect on instruction throughput
c) It increases instruction throughput by allowing more instructions to be executed in parallel
d) It reduces the number of instructions executed
Answer: c) It increases instruction throughput by allowing more instructions to be executed in parallel

Which of the following techniques helps reduce the complexity of out-of-order execution?
a) Increasing the clock speed
b) Simplifying the instruction set architecture
c) Using advanced branch prediction algorithms
d) Reducing the number of execution units
Answer: c) Using advanced branch prediction algorithms

What is the “instruction buffer” used for in out-of-order execution?
a) To store instructions before they are decoded
b) To hold instructions that are waiting to be executed
c) To manage memory accesses
d) To track the status of executed instructions
Answer: b) To hold instructions that are waiting to be executed

In out-of-order execution, what is meant by “commit stage”?
a) The stage where instructions are fetched from memory
b) The stage where instructions are executed
c) The stage where results are written back to the register file in program order
d) The stage where instructions are decoded
Answer: c) The stage where results are written back to the register file in program order

Which of the following is a common method to handle control hazards in out-of-order execution?
a) Data forwarding
b) Speculative execution
c) Register renaming
d) Instruction reordering
Answer: b) Speculative execution

What is the role of “instruction fetch” in out-of-order execution?
a) To reorder instructions for optimal execution
b) To retrieve instructions from memory for execution
c) To manage the instruction window size
d) To resolve data dependencies
Answer: b) To retrieve instructions from memory for execution

Which technique is commonly used to improve instruction-level parallelism in out-of-order execution?
a) Register renaming
b) Memory interleaving
c) Instruction buffering
d) Pipeline stalling
Answer: a) Register renaming

What is the primary function of the “instruction issue queue” in out-of-order execution?
a) To execute instructions
b) To manage and hold instructions until they are ready to be executed
c) To decode instructions
d) To fetch instructions from memory
Answer: b) To manage and hold instructions until they are ready to be executed

How does out-of-order execution affect power consumption in CPUs?
a) It decreases power consumption
b) It has no effect on power consumption
c) It can increase power consumption due to the complexity of scheduling and execution
d) It reduces power consumption by simplifying execution
Answer: c) It can increase power consumption due to the complexity of scheduling and execution

What is the purpose of “instruction retirement” in out-of-order execution?
a) To retire instructions that are no longer needed
b) To commit the results of executed instructions to the register file in program order
c) To fetch new instructions for execution
d) To decode instructions into machine code
Answer: b) To commit the results of executed instructions to the register file in program order

Which of the following best describes “data forwarding” in out-of-order execution?
a) Passing data between instructions that are not yet executed
b) Passing data between different execution units
c) Passing data directly from one instruction to another without waiting for intermediate results
d) Passing data from memory to registers
Answer: c) Passing data directly from one instruction to another without waiting for intermediate results

In out-of-order execution, what is meant by “dynamic instruction scheduling”?
a) Scheduling instructions at compile time
b) Scheduling instructions based on their readiness and availability during execution
c) Scheduling instructions based on fixed intervals
d) Scheduling instructions based on their order in the program
Answer: b) Scheduling instructions based on their readiness and availability during execution

Which of the following techniques is used to manage instruction dependencies in out-of-order execution?
a) Register renaming
b) Instruction fetching
c) Cache management
d) Branch prediction
Answer: a) Register renaming

What does “out-of-order execution” primarily aim to improve?
a) Instruction latency
b) Memory access time
c) Instruction throughput and pipeline efficiency
d) Clock speed
Answer: c) Instruction throughput and pipeline efficiency

Which component of out-of-order execution helps track the status of instructions?
a) Instruction fetch unit
b) Reorder buffer
c) Cache controller
d) Branch predictor
Answer: b) Reorder buffer

What does the term “out-of-order dispatch” refer to?
a) Dispatching instructions based on their program order
b) Dispatching instructions to execution units based on their readiness rather than their order in the program
c) Dispatching instructions to the instruction fetch unit
d) Dispatching instructions for decoding
Answer: b) Dispatching instructions to execution units based on their readiness rather than their order in the program

Which technique helps mitigate the effects of mispredicted branches in out-of-order execution?
a) Register renaming
b) Branch prediction
c) Data forwarding
d) Instruction buffering
Answer: b) Branch prediction

What is the role of the “branch predictor” in out-of-order execution?
a) To resolve data dependencies
b) To predict the outcome of branches to minimize pipeline stalls
c) To fetch instructions from memory
d) To decode instructions
Answer: b) To predict the outcome of branches to minimize pipeline stalls

What does “speculative execution” involve in out-of-order processors?
a) Executing only the most recent instructions
b) Executing instructions based on predicted paths and rolling back if predictions are incorrect
c) Executing instructions in the exact program order
d) Waiting for all dependencies to be resolved before execution
Answer: b) Executing instructions based on predicted paths and rolling back if predictions are incorrect

In out-of-order execution, what is meant by “instruction reordering”?
a) Reordering instructions after they have been executed
b) Reordering instructions in memory
c) Reordering instructions before execution to improve performance
d) Reordering instructions for instruction fetch
Answer: c) Reordering instructions before execution to improve performance

How does out-of-order execution impact instruction-level parallelism (ILP)?
a) It decreases ILP
b) It has no impact on ILP
c) It increases ILP by allowing instructions to be executed as soon as they are ready
d) It reduces the number of instructions that can be executed
Answer: c) It increases ILP by allowing instructions to be executed as soon as they are ready

Which component of an out-of-order CPU is responsible for issuing instructions to the execution units?
a) Instruction fetch unit
b) Reorder buffer
c) Instruction scheduler
d) Cache controller
Answer: c) Instruction scheduler

Out-of-Order Execution MCQs
By: Prof. Dr. Fazal Rehman Shamil | Last updated: September 20, 2024

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