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2 votes
2 votes
If page fault service time is 50 milli second  and memory access time is 100 ns, then what will be EMAT, if the probability of page fault is $p$ ?

a) $500000 + 100p$ ns

b) $100 + 500000p $ ns

c) $10^{-7} - 5 p\times 10^{-2}$ seconds

d) $10^{-7} + 49.9p \times 10^{-3}$ seconds

3 Answers

Best answer
4 votes
4 votes

EMAT = P (Page fault service time )+ (1-P)(Memory access time )

        $ = p(50\times 10^{-3} \times 10^9)$ns + $(1-p)(100)$ns

        $ = p( 50000000)$ns $+ 100$ns$ -100p$ns

        $= p(500000)\times 10^{-7}$sec $+ 10^{-7}$sec$- (10^{-7})p$ sec

        which is nearly equal to ... $10^{-7}$sec$ - 5p \times 10^{-2}$sec 

      Hence ans :Option C)

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7 votes
7 votes

Page fault service time includes memory access time too. So need to add it in case of page fault.

$\text{EMAT} =(1-p)10^{-4}+p \times 50 \text{ milliseconds}$

this gives d as ans

1 votes
1 votes
EMAT = P * 50000000 ns + (1-p) * 100 ns

          = 10^-7 +49.9*10^-3  (option D)

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