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GATE 2022 CS – Question 33

Computer Organization and Architecture · Memory Interfacing and Hierarchy · 1 mark · Numerical answer

A cache memory that has a hit rate of 0.8 has an access latency 10 ns and miss penalty 100 ns. An optimization is done on the cache to reduce the miss rate. However, the optimization results in an increase of cache access latency to 15 ns, whereas the miss penalty is not affected. The minimum hit rate (rounded off to two decimal places) needed after the optimization such that it should not increase the average memory access time is _____________.

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Correct answer: 0.85

Explanation

Before, AMAT $=10+0.2\cdot100=30$ ns. After, $15+(1-h)\cdot100\le30$ gives $1-h\le0.15$, so $h\ge0.85$.