Operating Systems · Question 28 · Hard
Operating Systems question 28
Memory access time is 200 ns, and servicing a page fault takes 8 ms. If 1 in every 1,000 memory accesses causes a page fault, what is the effective memory access time, approximately?
- 200 ns
- 1 microsecond
- 8.2 microseconds
- 80 microseconds
Answer and explanation
Answer: C. 8.2 microseconds
Explanation: EAT = (1 - p) × 200 ns + p × 8 ms = 0.999 × 200 + 0.001 × 8,000,000 ns = 199.8 + 8,000 ≈ 8,200 ns, about 8.2 microseconds. Even a rare page fault slows memory down roughly 40 times.
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