direct mapping and associative mapping cost

Question

Consider a cache consisting of 128 blocks of 16 words each. Main memory has 64 K words and given main memory is 16 bit addressable. Assume tag memory cost is defined as 1Rs/bit. X and Y are respective costs of tag memories (in Rs ) for Direct Mapping and Associative Mapping. The value (in Rs) of 2X + 3Y is
__________.

Comments

You are cirrect. Updating my answer.

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Tag memory for associative =5*128  =640(Y)

tag memory for direct mapp = 12*128= 1536(X)

so, 2(X)+3(Y)=3072+1920=4992

I am getting this...what wrong I did...

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For direct mapping address will have line bits and tag bits are 5 only. For associative tag bits are 12.

Answer 1

Size of tag memory is number of lines into number of bits for tag.

Therfore X= 2⁷× 5 is tag memory size in bits.

Now for associative mapping address format will be Tag | Offset. Bcoz for one set we do not need any bit. Y= 2⁷× 12

So answer is 5888 ₹

Comments

yeah got it I just interchanged those bits..thanks buddy