CO-Grand Test -Q6

Question

A processor with a word-addressable memory has a two-way set-associative cache. A cache line is one word, so a cache entry contains a set of two words. If there are M words of memory and C cache entries, how many words of memory map to the same cache entry?

(A) M / C

(B) 2M / C

(C) M / 2C

(D) M / 2

Answer 1

Block size = One word.

So M words of memory means M blocks.

A two-way set-associative cache. A cache line is one word, so a cache entry contains a set of two words.

Cache entry has been defined to be a set, not line. 

There are C cache entries in the cache, so, there are C Sets in the cache.

There are M blocks in main memory. 

In set-associative cache, if there are n sets then a block number B of main memory will go to the set number .

So, to each set, there will be 

         blocks which will map to each set(cache entry).

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Note that the number of words of memory map to the same cache line :

Inside a set, the block can go to any line,  So,         blocks map to a particular line in the cache.