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Suppose :

TLB lookup time = 20 ns

TLB HIT ratio = 80%

Memory access time = 75 ns

Swap page time = 500000 ns

50% pages are dirty and os uses a single level page table

a) what is EMAT if we assume page fault 0%?

b) what is EMAT if page fault 10% ?

In both cases assume cost to update TLB , page table , frame table is negligible (if needed).

1 Answer

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When page hit = 100%

{TLB hit(TLB time + Main Memory Access)}  +  {TLB miss(TLB time + Page Table Lookup + Main Memory Lookup)}

0.8(20+75) + 0.2(20+75+75) = 100ns

 

When page hit = 80%

{TLB hit(TLB time + Main Memory Access)}  +  {TLB miss[page hit(TLB time + Page Table Lookup + Main Memory Lookup)]  +  [page miss(TLB time + Page Table Lookup + page swap)]}

0.8(20+75) + 0.2([0.9(20+75+75)] + [0.1(20+75+500000)]) = 10108.6ns

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