GATE 2017 CS – Question 64
A cache memory unit with capacity of $N$ words and block size of $B$ words is to be designed. If it is designed as a direct mapped cache, the length of the TAG field is 10 bits. If the cache unit is now designed as a 16-way set-associative cache, the length of the TAG field is ________ bits.
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Correct answer: 14
Explanation
A 16-way set-associative cache has 16 times fewer sets than a direct mapped cache of the same size, so the index field is $\log_2 16 = 4$ bits shorter. The block offset and the address length do not change, so those 4 bits move into the tag. The tag length becomes $10 + 4 = 14$ bits.