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POCalculating actual/effective CPI for 3 level cache
 

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  1. POCalculating actual/effective CPI for 3 level cache
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    <p>(a) You are given a memory system that has two levels of cache (L1 and L2). Following are the specifications:</p> <ul> <li>Hit time of L1 cache: 2 clock cycles</li> <li>Hit rate of L1 cache: 92%</li> <li>Miss penalty to L2 cache (hit time of L2): 8 clock cycles</li> <li>Hit rate of L2 cache: 86%</li> <li>Miss penalty to main memory: 37 clock cycles</li> <li>Assume for the moment that hit rate of main memory is 100%.</li> </ul> <p>Given a 2000 instruction program with 37% data transfer instructions (loads/stores), calculate the CPI (Clock Cycles per Instruction) for this scenario.</p> <pre><code>For this part, I calculated it like this (am I doing this right?): (m1: miss rate of L1, m2: miss rate of L2) AMAT = HitTime_L1 + m1*(HitTime_L2 + m2*MissPenalty_L2) CPI(actual) = CPI(ideal) + (AMAT - CPI(ideal))*AverageMemoryAccess </code></pre> <p>(b) Now lets add another level of cache, i.e., L3 cache between the L2 cache and the main memory. Consider the following:</p> <ul> <li>Miss penalty to L3 cache (hit time of L3 cache): 13 clock cycles</li> <li>Hit rate of L3 cache: 81%</li> <li>Miss penalty to main memory: 37 clock cycles</li> <li>Other specifications remain as part (a) </li> </ul> <p>For the same 2000 instruction program (which has 37% data transfer instructions), calculate the CPI.</p> <pre><code>(m1: miss rate of L1, m2: miss rate of L2, m3: miss rate of L3) AMAT = HitTime_L1 + m1*(HitTime_L2 + m2*MissPenalty_L2) + m2*(HitTime_L3 + m3*MissPenalty_L3) </code></pre> <p>Is this formula correct and where do I add the miss penalty to main memory in this formula? It should probably be added with the miss penalty of L3 but I am not sure.</p>
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    1. COrelated discussion - http://stackoverflow.com/questions/20200129/how-to-calculate-effective-cpi-for-a-3-level-cache-homework
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