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In a paged memory management algorithm, the hit ratio is $70$%. If it takes $30$ nanoseconds to search Translation Look-aside Buffer (TLB) and $100$ nanoseconds (ns) to access memory, the effective memory access time is 

  1. $91$ ns
  2. $69$ ns
  3. $200$ ns 
  4. $160$ ns 
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3 Answers

Best answer
4 votes
4 votes

We can assume single level paging and TLB look and page table look happens sequentially meaning TLB look time is to be considered even for TLB miss. On a TLB miss we need to access main memory for getting the physical address for the page table before doing the actual memory access for the data. 

Effective access time = Hit ratio*Time during hit + Miss Ratio * Time During Miss

=0.7*(30+100) + 0.3 (30+100+100)

=91+69

=160 ns

Hence,Option(D)160ns is the correct choice.

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1 votes
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Effective access time = [%age of TLB (TLB time + Memory access time)]+[%age of Memory (TLB time+Memory access time+Memory access time)]

=0.7*(30+100) + 0.3 (30+100+100)

=91+69

=160 ns

Hence option is D
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Assume hierarchical access by default.

Also, UNLIKE CACHE, TLB DOES NOT HAVE ACTUAL DATA IN IT
 
So,$0.7[30+100] *0.3[30+100+100]=160$
 
Option D
Answer:

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