Speculative execution refers to:
A) Executing instructions before knowing if they are needed
B) Predicting the result of arithmetic operations
C) Delaying instructions until confirmed
D) Fetching data from memory after instruction execution
Answer: A
The main purpose of speculative execution is to:
A) Reduce power consumption
B) Increase instruction-level parallelism
C) Improve cache performance
D) Decrease memory latency
Answer: B
Speculative execution is often used in conjunction with:
A) Branch prediction
B) Register renaming
C) Cache coherence
D) Loop unrolling
Answer: A
A key challenge with speculative execution is:
A) Data hazards
B) Reverting incorrect speculative paths
C) Increasing clock cycles
D) Memory contention
Answer: B
Which of the following is a benefit of speculative execution?
A) Increased memory access time
B) Reduced pipeline complexity
C) Increased throughput
D) Simplified control flow
Answer: C
When a branch is mispredicted during speculative execution, the processor must:
A) Continue executing the speculated instructions
B) Flush the pipeline and discard speculative instructions
C) Store the speculative results in memory
D) Increase clock speed to recover
Answer: B
Speculative execution is most effective when:
A) The pipeline is short
B) The processor has multiple execution units
C) Branch mispredictions are frequent
D) Memory bandwidth is high
Answer: B
Which of the following is not related to speculative execution?
A) Out-of-order execution
B) Branch prediction
C) Cache prefetching
D) Compiler optimization
Answer: D
The speculative execution of instructions occurs:
A) After the branch outcome is confirmed
B) Before the branch outcome is known
C) Only if the branch is taken
D) After memory access
Answer: B
One disadvantage of speculative execution is:
A) Increased energy consumption
B) Reduced instruction parallelism
C) Decreased clock frequency
D) Simpler hardware requirements
Answer: A
Speculative execution works by:
A) Predicting memory locations
B) Executing multiple instructions along different paths
C) Executing instructions sequentially
D) Delaying execution until branch results are known
Answer: B
The rollback mechanism in speculative execution is used when:
A) The branch prediction is incorrect
B) The execution finishes early
C) The memory access is delayed
D) The ALU encounters an error
Answer: A
Which of the following is required for effective speculative execution?
A) Low power consumption
B) Accurate branch prediction
C) Simple control flow
D) High memory latency
Answer: B
Speculative execution helps in reducing:
A) Control hazards
B) Data hazards
C) Cache misses
D) Arithmetic errors
Answer: A
The performance improvement from speculative execution depends on:
A) Cache size
B) Instruction window size
C) Branch prediction accuracy
D) Number of ALUs
Answer: C
When speculation is incorrect, the CPU must:
A) Store the incorrect results in memory
B) Flush the speculative instructions and restart
C) Pause the pipeline until the correct path is determined
D) Execute both speculative and non-speculative paths
Answer: B
Which type of instructions are typically executed speculatively?
A) Arithmetic instructions
B) Memory load/store instructions
C) Control flow instructions
D) Floating-point instructions
Answer: C
In speculative execution, when a branch is taken, the processor:
A) Continues executing along the speculative path
B) Flushes the pipeline and starts executing the correct path
C) Switches to the non-speculative path
D) Waits for the memory access to complete
Answer: B
Speculative execution allows modern processors to:
A) Reduce the number of instructions
B) Avoid pipeline stalls
C) Simplify branch handling
D) Improve cache coherence
Answer: B
Which of the following is an example of speculative execution in modern processors?
A) Prefetching data into cache
B) Executing both sides of a conditional branch
C) Delaying branch instructions
D) Limiting instruction parallelism
Answer: B
A speculative instruction is typically:
A) Committed only when the branch outcome is verified
B) Immediately executed regardless of branch outcome
C) Always stored in memory
D) Ignored if the branch is not taken
Answer: A
Speculative execution can be used to:
A) Execute instructions in-order
B) Increase cache hit rate
C) Maximize pipeline utilization
D) Minimize arithmetic errors
Answer: C
Which of the following is true about speculative execution in superscalar processors?
A) It decreases branch prediction accuracy
B) It increases the number of pipeline flushes
C) It improves instruction-level parallelism
D) It reduces the number of functional units needed
Answer: C
The effectiveness of speculative execution decreases when:
A) Branch prediction accuracy is low
B) Instruction fetch is fast
C) Cache size is large
D) Memory latency is reduced
Answer: A
One of the risks of speculative execution is:
A) Lower throughput
B) Incorrect instruction execution
C) Delayed instruction fetch
D) Instruction prefetching
Answer: B
Speculative execution increases hardware complexity because it requires:
A) Additional functional units
B) The ability to rollback mispredicted instructions
C) Simplified instruction pipelines
D) Fewer branch instructions
Answer: B
When a speculatively executed instruction is wrong, the processor must:
A) Store the result in memory
B) Flush the pipeline and discard the instruction
C) Delay execution of subsequent instructions
D) Restart the entire pipeline
Answer: B
Speculative execution improves performance primarily in:
A) Sequential instruction execution
B) Memory-bound applications
C) Control-heavy and branch-intensive programs
D) Data-intensive applications
Answer: C
Speculative execution is crucial for:
A) RISC architectures
B) SIMD processors
C) Out-of-order execution
D) Single-cycle processors
Answer: C
Speculative execution relies on the assumption that:
A) Memory accesses are predictable
B) Cache hits will occur
C) The predicted path of execution is correct
D) The processor has a fixed pipeline depth
Answer: C
The cost of incorrect speculative execution includes:
A) Reduced branch prediction accuracy
B) Additional energy usage and pipeline flushes
C) Higher clock speeds
D) Simplified execution flow
Answer: B
One advantage of speculative execution is:
A) Lower power consumption
B) Reduced cache miss rate
C) Increased instruction throughput
D) Decreased hardware complexity
Answer: C
Speculative execution can increase energy consumption because:
A) It requires frequent memory accesses
B) More instructions are executed than necessary
C) Branch prediction is always incorrect
D) The pipeline must be frequently flushed
Answer: B
In speculative execution, a “commit” refers to:
A) Writing results to the register or memory once speculation is confirmed
B) Storing speculative results in a temporary buffer
C) Discarding incorrect speculative results
D) Prefetching speculative instructions
Answer: A
The benefit of speculative execution is maximized when:
A) There are few branch instructions
B) Memory access time is low
C) The branch prediction is highly accurate
D) Instructions are executed sequentially
Answer: C
When speculative execution is mispredicted, the processor must:
A) Pause execution of all subsequent instructions
B) Execute both speculative and non-speculative paths
C) Rollback and restart from the correct path
D) Flush the cache and prefetch the next instructions
Answer: C
Which of the following is critical for minimizing the drawbacks of speculative execution?
A) Large cache size
B) Accurate branch prediction
C) Increased memory bandwidth
D) Simplified control logic
Answer: B
Speculative execution can improve performance by:
A) Reducing the number of executed instructions
B) Increasing pipeline utilization
C) Reducing power consumption
D) Simplifying control hazards
Answer: B
In speculative execution, the processor:
A) Waits for the outcome of branches before continuing
B) Executes instructions along the predicted path
C) Ignores branches until execution completes
D) Always executes instructions in-order
Answer: B
A speculative instruction is:
A) Discarded if incorrect but committed if correct
B) Always executed regardless of correctness
C) Executed after branch outcome is confirmed
D) Stored in a temporary buffer until required
Answer: A
When speculative execution is incorrect, the processor experiences:
A) Reduced instruction parallelism
B) Pipeline flush and performance penalty
C) Increased clock frequency
D) Simplified execution flow
Answer: B
In modern CPUs, speculative execution is key to achieving:
A) High clock speeds
B) Instruction-level parallelism
C) Memory coherence
D) Reduced cache misses
Answer: B
Which of the following makes speculative execution more effective?
A) Reduced branch prediction
B) Deeper pipelines
C) Highly accurate branch predictors
D) Fewer functional units
Answer: C
Speculative execution can lead to security vulnerabilities, such as:
A) Cache misses
B) Side-channel attacks
C) Instruction prefetching
D) Cache coherence issues
Answer: B
Speculative Execution MCQs