为什么我们不需要在这个问题中减去字节偏移位？

Question

In the following question: How to find tag bit in cache given word address

They have found the number of tag bits by 32 - number of index bits - word offset . But in the book, they also mentioned the following:

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Why are we not subtracting 2 here in the problem?

Answer 1

For anyone who is getting confused like me, it is as follows as far as I know.

Given word address 3 , we can convert it to by address which is one of address between 12 and 15 inclusive because word is 4 bytes and thus you have to multiply word address by 4.

If you convert 12 and 15 to binary it will be ...001100 and ...001111 and you have to get least 2 significant bits for byte offset and the next 1 bit for word( block) offset which leaves 001 in both cases.