Virtual Labs

MSI Cache Coherence Protocol

After completing the MSI simulation, what can you conclude about the Invalid (I) state?

a: It represents the initial state and any cache line that is not valid in the current cache Explanation

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b: It is the most efficient state for all operations Explanation

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c: It can only be reached from the Modified state Explanation

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d: It allows direct read and write operations Explanation

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Based on the simulation results, which cache state allows for the most efficient read operations?

a: Invalid state Explanation

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b: Modified state only Explanation

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c: None of the states allow efficient reads Explanation

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d: Both Modified and Shared states Explanation

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What did you observe about write operations to cache lines in Shared state during the simulation?

a: They complete without any bus activity Explanation

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b: They require a BusUpgr transaction to invalidate other copies Explanation

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c: They are not allowed in MSI protocol Explanation

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d: They automatically convert all other caches to Modified state Explanation

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From your simulation experience, what happens when a processor reads a memory location that another processor has in Modified state?

a: The processor with Modified state writes back to memory and both transition to Shared state Explanation

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b: The read fails until the modified data is written to memory Explanation

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c: Both processors end up with the data in Modified state Explanation

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d: The requesting processor gets stale data from memory Explanation

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Based on your simulation observations, what is the key difference between BusRd and BusRdX transactions?

a: BusRdX requests exclusive access, BusRd requests shared access Explanation

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b: BusRd is for writes, BusRdX is for reads Explanation

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c: BusRdX is faster than BusRd Explanation

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d: There is no functional difference between them Explanation

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During the simulation, when did you observe the highest bus traffic?

a: When processors read data already in their caches Explanation

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b: When processors access completely different memory addresses Explanation

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c: When processors frequently write to the same memory locations Explanation

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d: When processors are idle Explanation

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What insight about cache performance did you gain from analyzing the hit/miss ratios in the simulation?

a: Miss ratio is always zero in multiprocessor systems Explanation

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b: Coherence protocol operations can convert hits to misses Explanation

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c: Write operations never affect cache performance Explanation

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d: Cache performance is independent of access patterns Explanation

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Considering a real-world scenario, if you observed frequent state transitions in your simulation, what would be the most likely cause and solution?

a: Insufficient cache size; solution is to increase cache associativity only Explanation

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b: False sharing where different processors access different parts of the same cache line; solution is to restructure data layout Explanation

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c: Too many processors; solution is to reduce the number of cores Explanation

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d: Slow memory; solution is to increase memory frequency only Explanation

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Based on your simulation experience, how would you optimize a program to minimize cache coherence overhead?

a: Minimize shared data access and use thread-local data structures when possible Explanation

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b: Use as many shared variables as possible to increase data sharing Explanation

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c: Always write to memory instead of cache to avoid coherence Explanation

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d: Increase the frequency of synchronization operations Explanation

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