Consider a 4-way set associative cache consisting of 128 lines with a line size of 64 words. The CPU generates a 20-bit address of a word in main memory. The number of bits in the TAG, LINE and WORD fields arerespectively:

(A) 9,6,5
(B) 7, 7, 6
(C) 7, 5, 8
(D) 9, 5, 6


Answer: (D)

Explanation:

Here the number of sets = 128/4 = 32 (as it is 4 say set associative)

We have total 64 words then we need 6 bits to identify the word

So the line offset is 5 bits and the word offset is 6 bits

and the TAG = 20-(5+6) =9 bits

so it should be 9,5,6

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