Write Policies (Write-Through, Write-Back) MCQs

What is the primary characteristic of the “write-through” cache policy?
a) Data is written to both the cache and the main memory simultaneously
b) Data is only written to the cache and not to the main memory
c) Data is written to the main memory only when the cache line is evicted
d) Data is cached and updated in main memory on a delay basis
Answer: a) Data is written to both the cache and the main memory simultaneously

Which write policy ensures that data is only updated in the cache and written back to the main memory only when the cache line is evicted?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What advantage does the “write-back” cache policy offer over “write-through”?
a) Reduces the number of write operations to the main memory, potentially improving performance
b) Ensures immediate consistency between the cache and the main memory
c) Simplifies cache coherence protocols
d) Increases the speed of data retrieval from the main memory
Answer: a) Reduces the number of write operations to the main memory, potentially improving performance

In which scenario is the “write-through” cache policy most advantageous?
a) When immediate consistency between the cache and the main memory is required
b) When reducing memory write operations is a priority
c) When minimizing the number of cache line evictions is important
d) When the system can tolerate delays in data consistency
Answer: a) When immediate consistency between the cache and the main memory is required

Which write policy is likely to generate more bus traffic in a multiprocessor system?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

How does the “write-back” policy affect the cache’s performance in terms of write operations?
a) It reduces the number of write operations to the main memory, potentially improving overall performance
b) It increases the frequency of writes to the main memory
c) It ensures immediate updates to all caches
d) It increases the complexity of cache coherence management
Answer: a) It reduces the number of write operations to the main memory, potentially improving overall performance

Which write policy would be preferred if minimizing write latency to the main memory is crucial?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: b) Write-back

What is a significant drawback of the “write-back” policy compared to “write-through”?
a) Data in the cache may become stale if not promptly written back to main memory
b) It generates more frequent write operations to main memory
c) It requires immediate consistency between cache and main memory
d) It increases bus traffic
Answer: a) Data in the cache may become stale if not promptly written back to main memory

Which policy is generally used to ensure that all data modifications are immediately reflected in the main memory?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

How does the “write-back” policy help in reducing write traffic to main memory?
a) By updating the main memory only when a cache line is evicted, not on every write
b) By immediately writing every change to main memory
c) By delaying all writes until the system is idle
d) By using a different cache line size
Answer: a) By updating the main memory only when a cache line is evicted, not on every write

Which write policy could potentially lead to a higher risk of data loss in case of a system crash?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What does the “write-through” policy ensure in terms of data consistency?
a) Immediate consistency between the cache and main memory
b) Delayed consistency between the cache and main memory
c) Data consistency only when cache lines are evicted
d) Increased data latency in the cache
Answer: a) Immediate consistency between the cache and main memory

Which write policy is more suitable for systems where data consistency is critical and must be maintained at all times?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

In which write policy are cache lines updated in the main memory only when they are evicted from the cache?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

How does “write-through” affect overall system performance compared to “write-back”?
a) It may decrease performance due to the need to write data to main memory with every cache update
b) It improves performance by reducing the number of write operations
c) It simplifies cache coherence protocols
d) It eliminates the risk of data becoming stale
Answer: a) It may decrease performance due to the need to write data to main memory with every cache update

Which write policy is less complex to implement in terms of cache coherence protocols?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What is a common advantage of using the “write-back” cache policy in a high-performance computing system?
a) It reduces memory write traffic, which can enhance performance
b) It ensures all data is immediately updated in main memory
c) It simplifies cache management by reducing the number of states
d) It guarantees data consistency at all times
Answer: a) It reduces memory write traffic, which can enhance performance

Which policy involves writing data to the cache and the main memory simultaneously with every update?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What could be a major disadvantage of using the “write-through” policy in a system with high write activity?
a) It may result in increased bus traffic and slower overall performance
b) It may simplify cache coherence management
c) It reduces the risk of data inconsistency
d) It enhances cache performance by reducing write latency
Answer: a) It may result in increased bus traffic and slower overall performance

Which write policy is likely to lead to more consistent data across multiple caches in a multiprocessor system?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What is a disadvantage of the “write-back” policy when compared to “write-through” in terms of data consistency?
a) The cache data might become stale and inconsistent with the main memory until written back
b) It requires more frequent updates to the main memory
c) It complicates the implementation of cache coherence protocols
d) It increases the frequency of cache line eviction
Answer: a) The cache data might become stale and inconsistent with the main memory until written back

Which policy would be more efficient in a system where writes to the main memory are infrequent and performance is critical?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

How does the “write-back” policy affect cache coherence compared to “write-through”?
a) It requires more complex coherence protocols due to potential data inconsistency
b) It simplifies the coherence protocols by ensuring all data is immediately updated
c) It eliminates the need for cache coherence protocols
d) It automatically synchronizes all caches
Answer: a) It requires more complex coherence protocols due to potential data inconsistency

Which write policy involves updating main memory on every write operation to the cache?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What is the impact of the “write-back” policy on cache performance in terms of data writes?
a) It can enhance performance by reducing the number of writes to the main memory
b) It can degrade performance by increasing write operations
c) It ensures immediate synchronization with main memory
d) It simplifies data management
Answer: a) It can enhance performance by reducing the number of writes to the main memory

Which write policy would be best suited for applications with high write-throughput requirements and a need for immediate data consistency?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

How does the “write-back” policy affect the cache-to-main-memory update process?
a) Data is updated in main memory only when the cache line is evicted, not on every write
b) Data is updated in both cache and main memory simultaneously
c) Data is updated in main memory only when the cache is idle
d) Data is not written to the main memory at all
Answer: a) Data is updated in main memory only when the cache line is evicted, not on every write

Which write policy would be less suitable for a system where data consistency must be maintained at all times?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

In a system with a “write-through” policy, what happens to data when a cache line is updated?
a) Data is written to both the cache and the main memory simultaneously
b) Data is written only to the cache and updated in main memory later
c) Data is kept only in the cache until the line is evicted
d) Data is delayed until the system is idle
Answer: a) Data is written to both the cache and the main memory simultaneously

What is a key difference between the “write-through” and “write-back” cache policies?
a) Write-through updates main memory immediately, while write-back updates it only on eviction
b) Write-back updates main memory immediately, while write-through updates it on eviction
c) Write-through only updates the cache, while write-back updates both cache and memory
d) Write-back updates memory more frequently than write-through
Answer: a) Write-through updates main memory immediately, while write-back updates it only on eviction

Which write policy provides more immediate data consistency but can lead to higher write latency?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

How does the “write-back” policy affect the frequency of memory writes in a system?
a) It decreases the frequency of writes to main memory, potentially improving performance
b) It increases the frequency of writes to main memory
c) It ensures writes are synchronized with main memory immediately
d) It avoids writes to main memory altogether
Answer: a) It decreases the frequency of writes to main memory, potentially improving performance

Which write policy ensures that every write operation updates both the cache and the main memory, ensuring immediate consistency?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

In a “write-back” policy, what happens to the data in the cache when it is modified?
a) The data is not written to the main memory until the cache line is evicted
b) The data is immediately updated in both the cache and main memory
c) The data is updated only in the main memory
d) The data is cached and not written to any storage
Answer: a) The data is not written to the main memory until the cache line is evicted

Which cache policy would likely result in lower main memory write traffic in a system?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What impact does the “write-through” policy have on the cache line eviction process?
a) It does not directly affect the eviction process but ensures immediate memory updates
b) It simplifies the eviction process by reducing the need for synchronization
c) It requires data to be written back to main memory during eviction
d) It delays the eviction process to ensure data consistency
Answer: a) It does not directly affect the eviction process but ensures immediate memory updates

Which write policy is more likely to cause data inconsistencies if not managed properly?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What does the “write-back” policy typically do when a cache line is evicted?
a) It writes the updated data from the cache to the main memory
b) It discards the data in the cache without updating the main memory
c) It reads new data into the cache from the main memory
d) It invalidates the data in the cache
Answer: a) It writes the updated data from the cache to the main memory

Which policy is likely to be favored in systems where write operations are less frequent, but performance is critical?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What is a common advantage of the “write-through” policy for data consistency?
a) It ensures that data in both the cache and main memory is always consistent
b) It reduces the number of memory writes
c) It decreases cache hit rates
d) It improves cache performance by delaying updates
Answer: a) It ensures that data in both the cache and main memory is always consistent

Which write policy would be more suitable for a scenario where minimizing the number of main memory writes is a priority?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

How does the “write-back” policy impact the coherence of data between caches and main memory?
a) It requires more complex protocols to manage data coherence due to potential inconsistencies
b) It simplifies coherence management by ensuring data is immediately consistent
c) It eliminates the need for cache coherence protocols
d) It automatically synchronizes data across all caches
Answer: a) It requires more complex protocols to manage data coherence due to potential inconsistencies

What is a drawback of using “write-through” policy in systems with high data modification rates?
a) Increased bus traffic and potential performance degradation
b) Reduced data consistency
c) Higher risk of data staleness
d) More complex cache coherence management
Answer: a) Increased bus traffic and potential performance degradation

Which policy involves immediate updates to main memory for every write operation, thus reducing the complexity of cache coherence?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What is the main disadvantage of the “write-back” policy in terms of data synchronization?
a) It can lead to stale data if cache lines are not written back promptly
b) It increases write latency to the main memory
c) It ensures immediate data consistency
d) It simplifies cache management
Answer: a) It can lead to stale data if cache lines are not written back promptly

Which write policy is advantageous for applications that require frequent writes but can tolerate data staleness?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

In the context of cache policies, what is a common benefit of “write-back” over “write-through”?
a) It reduces the number of write operations to the main memory, potentially improving performance
b) It ensures that every write operation is immediately reflected in main memory
c) It simplifies the implementation of cache coherence protocols
d) It reduces the risk of data becoming stale
Answer: a) It reduces the number of write operations to the main memory, potentially improving performance

Which write policy would be less complex in terms of maintaining cache coherence across multiple processors?
a) Write-through
b) Write-back
c) Write-invalidate
d) Write-update
Answer: a) Write-through

What effect does the “write-back” policy have on the cache-to-main-memory write operations?
a) It defers writing changes to main memory until cache lines are evicted
b) It writes changes to main memory immediately with every cache update
c) It writes to main memory less frequently than the write-through policy
d) It eliminates write operations to main memory entirely
Answer: a) It defers writing changes to main memory until cache lines are evicted

Which write policy can be advantageous in systems with high-frequency writes and lower data consistency requirements?
a) Write-back
b) Write-through
c) Write-invalidate
d) Write-update
Answer: a) Write-back

What is a primary reason for choosing the “write-through” policy in a system requiring strict data consistency?
a) It ensures immediate updates to main memory, maintaining data consistency
b) It reduces the frequency of writes to main memory
c) It improves cache performance by delaying updates
d) It simplifies the implementation of cache management protocols
Answer: a) It ensures immediate updates to main memory, maintaining data consistency

Write Policies (Write-Through, Write-Back) MCQs

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