Effective memory access time

Question

please explain how to understand this problem

Comments

EMAT= TLB Hit ( cache access time + memory access time) + TLB miss ( cache access time + 3* main mem access time )
why ?
3* main mem access time  becoz
2 main mem access time for page tables + 1 for data access

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Just follow the hierarchy of accessing the memory.

Firstly we will go to the TLB, if there's is hit (got frame no) we move to memory, if there's is miss in TLB, we look into page table which is in memory (two times) because 2 level paging and then finally to memory after we got frame no from outer page table

EMAT= 0.9*(3+50)+0.1*(3+50+50+50)

EMAT = 63 ns

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what is the same question is for a cache?

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If cache is introduced then before going into memory we will first look into cache, if there's is miss in cache then only we look into memory otherwise in cache in case of hit.

We can write EMAT as

EMAT = TLB hit(TLB access+cache hit*cache access+ cache miss(cache access + memory Acces) + TLB miss( TLB access+ memory Acces + memory Acces + cache hit* cache access + cache miss( cache access+ memory miss)

Here we are assuming that page reside in main memory not in cache memory.