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Consider a single-level cache with an access time of 1.8ns, a line size of 16 bytes, and a hit ratio of 0.85. Main memory uses a block transfer capability that has a first word (4 bytes) access time of 40 ns and an access time of 5 ns for each word thereafter.

Suppose that increasing the line size to 64 bytes increases the hit ratio to 0.95. What is the average memory access time?

  1. 9.55ns
  2. 8.55ns
  3. 7.55ns
  4. 10.75ns

I know the answer is 7.55ns

while calculating the Main Memory Access time = 40ns(first 4 bytes) + 75 (remaining 60 bytes)

How it get 75ns accesstime ? After 4 words each words is accessed at 5ns Access time.?

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