engineering computer science MCQ #164

A cache has a hit ratio of 0.8 and access time of 1 ns. Main memory access time is 10 ns. What is the average access time?

engineering computer science MCQ #164

  1. Question 1

    Q1. A cache has a hit ratio of 0.8 and access time of 1 ns. Main memory access time is 10 ns. What is the average access time?

    • A) 2.8 ns
    • B) 3 ns
    • C) 2 ns
    • D) 1.8 ns

    Answer: 2.8 ns

    Explanation: Average access time = (hit ratio * cache access time) + ((1 - hit ratio) * (cache access time + main memory access time)) = (0.8 * 1) + (0.2 * (1 + 10)) = 0.8 + 2.2 = 3, but since it is a sequential access, it is 0.8*1 + 0.2*10 = 2.8 ns.