Let HT1, MR1, and MP1 be the hit time, miss rate, and miss penalty for a one-lev

Question

Let HT1, MR1, and MP1 be the hit time, miss rate, and miss penalty for a one-level cache.

a. Compute average memory access time (AMAT) for the cache if HT1 = 10ns, MR1 = 4%, and MP1 = 100 ns.

b. Compute the speedup in AMAT of the one-level cache relative to a memory with no cache.

c. Derive the equation for AMAT for a two-level cache If HT2, MR2, and MP2 are the hit time, hit rate, and miss penalty for the second level of the cache.

d. Compute AMAT for the two-level cache if HT2 = 20ns, the global miss rate is 2%, and MP2 = 100 ns.

e. Compute the speedup in AMAT of the two-level cache relative to the one-level.

Explanation / Answer

[a] AMAT = Hit Rate * Hit time + Miss Rate * Miss Time
           = 10 * 96% + 100 * 04%
           =   9.6 + 4
          =   13.6 ns

[d] 20 * 98 + 100 * 2
     = 19.6 + 2
     = 21.6 ns

[e] Speedup = Time (old) / Time (new)
                    = 13.6 / 21.6
                    = 0.62

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