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GATE 2017 CS (CS2) – Question 39

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

L₁ and L₂ cache access times are 1 and 8 cycles. L₂-to-main-memory miss penalty is 18 cycles. L₁ miss rate is twice L₂ miss rate. AMAT is 2 cycles. Find the respective miss rates.

  1. 0.111 and 0.056
  2. 0.056 and 0.111
  3. 0.0892 and 0.1784
  4. 0.1784 and 0.0892

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Correct answer: (A) 0.111 and 0.056

Explanation

Let the L₂ local miss rate be m, so L₁ misses with 2m. Then $2=1+2m(8+18m)$, giving 36m²+16m−1=0. Its positive root is 1/18≈0.05556; L₁ rate is 1/9≈0.11111. Hence A.

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