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Consider a system with a two-level paging scheme in which a regular memory access takes 150 ns and servicing a page fault takes 8 ms. An average instruction takes 100 ns of CPU time, and two memory accesses. The TLB hit ratio is 90%, and the page fault rate is one in every 10,000 instructions. What is the effective average instruction execution time?
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- 645 ns
- 1050 ns
- 1215 ns
- 1230 ns
- 645 ns
Correct Option: D
Memory access time = 0.90 × 150 + 0.10 × (150 + 150)
= 135 + 30 = 165 ns
The error rate = 1 / 10000 = 10–4
CPU burst time = 100 ns
Total execution time = [100 + 2[165] +10 – 4 × 8 × 106]
= 100 + 330 + 800
= 100 + 1130 = 1230 ns
Hence (d) is correct option.
