58. A system has a memory access time of 50 ns and a cache access time of 2 ns. The instruction time is 4 ns (not counting memory access) and the average instruction requires 0.25 memory accesses. If the hit ratio is 0.90, what is the average instruction time?

What will be an ideal response?

The average time is 4 ns (instruction) + 0.25 (memory access rate) × (htc + (1 ? h)tm)
= 4.0 + 0.25 (0.9 × 2 + 0.1 × 50) = 4.0 + 0.25(1.8 + 5.0) = 4.0 + 0.25 × 6.8 = 5.7 ns.