Question

Let the page fault service time be 10 ms in a computer with average memory access time being 20 ns. If one page fault is generated for every 10⁶ memory accesses, what is the effective access time for the memory?

1. 21.4 ns
2. 29.9 ns
3. 23.5 ns
4. 35.1 ns

Answer 1

Correct Answer - Option 2 : 29.9 ns

Data:

page fault service time = S = 10 ms = 10⁷ ns

page fault rate = p = \(\frac{1}{10^{6}}\)

memory access time = m = 20 ns

Formula:

Effective access time (EAT) = p × S + (1 - p) × m

Calculation:

EAT = \(\frac{1}{10^{6}}\)× 10⁷ + (1 - \(\frac{1}{10^{6}}\)) × 20

EAT = 29.99 ns