Made Easy CBT

Question

Consider simple paging with TLB. The TLB hit ratio is 60%. If there is hit, it takes 80ns for a memory reference otherwise it takes 130ns for a memory reference. If the Effective memory access time with TLB is 100ns, then the aceess time of TLB is ______?

The answer mentioned is 30ns. They have taken TLB and Mem Access time as memory reference. But I think memory reference should not include TLB access time.

Comments

@Shobhit Joshi thanks for the clarification.. So does that mean it will be stated whether we have to include t or not because in some questions related to cache and tlb we are using it while in some we arent and as there is no such diff in the manner the ques are framed.. So what should we do in such a case?

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Depends on the question i guess, if the given method uses TLB or not, or the memory reference includes TLB time like in this question. Mostly the memory reference and TLB access are separately given, or if they include it will be separately mentioned i guess.

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If we do not consider t+m as 80 and only 80 as m ,,then we will not be able to solve the question.

Answer 1

It's kind of ambiguous wording used here,it's memory reference takes 80ns when tlb hit which means m=80 and when miss it's 130 ns which don't make sense but when you put in the equation, 100=0.6(X+80)+0.4(X+130), you'll get X=0, which means tlb time is included(atleast that's what I understood 😆), which means X+m=80ns and X+2m=130, solve the equation and you'll get x and m.