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GATE 2021 CS (CS2) – Question 37

Computer Organization and Architecture · Memory Interfacing and Hierarchy · 2 marks · Multiple choice

L1 and larger L2 form an inclusive cache hierarchy. S1: Read misses in a write-through L1 never cause dirty-line writebacks to L2. S2: Write-allocate must be used with write-through and no-write-allocate with writeback. Which are true?

  1. S1 true,S2 false
  2. S1 false,S2 true
  3. Both
  4. Neither

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Show answer and explanation

Correct answer: (A) S1 true,S2 false

Explanation

Write-through immediately propagates L1 writes, so L1 has no dirty modified-only copies needing writeback on a read-miss replacement. Thus S1 is true. Allocation on a write miss is a separate policy choice; the asserted mandatory pairing in S2 is false, and common pairings are often the opposite. Answer A.

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