MADEEASY- CO - SET Associative mapping

Question

Assume a new cache design is proposed by a student. But he later discovered design has too many conflict misses and to resolve this issue he increases the associativity in the design.

Which of the following implication will occur in the new design ?

  A. Access time increases

  B. Index bit increases

  C. No implications in the design

 

what does INDEX bits refers to in set associative and associative mapping?

Comments

I think these are set bits in case of set associative. But we don't have any such in associative.

---

@Hemanth_13, OK , but my doubt is
Indexing refers to getting the location of the particular word, so in set associative, even if we get the set, still there are many blocks withing that set, so we still need to add the associative bits then?

---

Indexing refers to getting the location of the particular word,

Indexing refers to getting the set only.

===> when associativity increases, automatically number of sets decreased ==> no.of bits to represent sets are may decrease but never increase

---

@Markzuck

By the way type the question instead of screenshot !

Answer 1

For set associative mapping it refers to set bits. For associative mapping no index bit exist. 

Here as we increase k in set associative mapping no of bits required to represent k decreases. ( no of bits required to address sets = No of CM block/ k). So B is wrong.

If we increase the number of sets below then also access time wouldn't change as accessing all blocks in set and then tag comparison for all of them are done in parallel. So A is wrong.

Good read: https://courses.cs.washington.edu/courses/cse378/02sp/sections/section9-2.html

Ref: https://www.sciencedirect.com/topics/computer-science/set-associative-cache