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Cache Memory and Hierarchy

GATE CSE 2017 Set 1 · Q25

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Consider a two-level cache hierarchy with L1 and L2 caches. An application incurs 1.4 memory accesses per instruction on average. For this application, the miss rate of L1 cache is 0.1; the L2 cache experiences, on average, 7 misses per 1000 instructions. The miss rate of L2 expressed correct to two decimal places is ________.

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Official answer: 0.05 (±0)

Cache Memory and Hierarchy

Let the total number of instructions executed be N=1000N = 1000.

  1. Total Memory Accesses to L1:

    Total L1 Accesses=1.4×N=1.4×1000=1400\text{Total L1 Accesses} = 1.4 \times N = 1.4 \times 1000 = 1400
  2. Number of L1 Misses (which become accesses to L2):

    L1 Misses=Miss Rate of L1×Total L1 Accesses=0.1×1400=140\text{L1 Misses} = \text{Miss Rate of L1} \times \text{Total L1 Accesses} = 0.1 \times 1400 = 140
  3. Number of L2 Misses: Given as 7 misses per 1000 instructions, so for N=1000N = 1000:

    L2 Misses=7\text{L2 Misses} = 7
  4. Local Miss Rate of L2 Cache:

    Miss Rate of L2=Number of L2 MissesNumber of L2 Accesses=7140=120=0.05\text{Miss Rate of L2} = \frac{\text{Number of L2 Misses}}{\text{Number of L2 Accesses}} = \frac{7}{140} = \frac{1}{20} = 0.05

Thus, the miss rate of L2 is 0.05.

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This Cache Memory and Hierarchy previous year question is Q25 of the GATE CSE 2017 Set 1 paper. Find more GATE CSE PYQs on Cache Memory and Hierarchy in Computer Organization and Architecture, or browse all GATE CSE PYQs.

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Cache Memory and Hierarchy in GATE CSE

Cache Memory and Hierarchy has 47 GATE CSE PYQs across 23 papers from 2011 to 2026. 7 of them are 1-mark NAT questions like this one, and GATE CSE 2017 Set 1 has 3.

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GateAI solution cardGATE CSE 2017 Set 1 · Q25 · NAT

Consider a two-level cache hierarchy with L1 and L2 caches. An application incurs 1.4 memory accesses per instruction on average. For this application, the miss rate of L1 cache is 0.1; the L2 cache experiences, on average, 7 misses per 1000 instructions. The miss rate of L2 expressed correct to two decimal places is …

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