Q48,Paper 2,J13.Let the page fault service time be 10 millisecond(ms) in a computer with Average memory access time being 20 nanosecond(ns). If one page fault is generated for every 10^6memory accesses, what is the effective access time for memory ?

(A) 21 ns

(B) 23 ns

(C) 30 ns

(D) 35 ns

Answer A.

Explanation.

Let there are 10⁶+1memory address. It generated 1 fault . fault take 10^-3 s+(20*10^-9)s.

Remaining memory access will take time.(20*10^-9*10⁶).

Total time is  10^-3 +(20*10^-9)+ (20*10^-9*10⁶).=  10^-9(1+20*10^-6+20)

                                    10⁶+1              

Approximately 21 ns.