Problem 1. Consider a Demand paging system with a paging disk that has an averag

Question

Problem 1.

Consider a Demand paging system with a paging disk that has an average access and transfer time of 30 milliseconds. Addresses are translated through a page table in main memory, with an access time of 5 microseconds per memory access. Thus, each memory reference through the page table takes two accesses. To improve this time, we have added an associative memory (TLB) that reduces access time to one memory reference if the page-table entry is in the associative memory. Assume that 82% of the accesses are in the associative memory and that, of those remaining, 18% cause page faults. What is the effective memory access time (EAC)?

Explanation / Answer

Effective memory access time is calculated by following way.

Hit ratio = 82% = 0.82

Main Memory access time = 30

Associative Lookup (TLB access) = 5

The formula for EAC is

So calculation is as follows.

EAC = (0.05)*(100 + 30) + (1 - 0.05) (30 + 100*2 + 100)

EAC = 319.5ns

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