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Consider the given two statements S1 and S2

S1: If compulsory misses are most common then the designers should consider to increase the cache line size to take better advantage of locality.

S2: If capacity misses are most common then the designer should increase the cache associativity, in order to provide more flexibility when collision occurs.

Which of the following is correct?

  1. S1 is true, S2 is false
  2. S2 is true, S1 is false
  3. Both are false
  4. Both are true
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3 Answers

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A) is the answer

1st one

Compulsory misses means first time access to a cache block. By increasing the block size, this can be reduced as this location might be fetched as part of a previous cache miss.

https://gateoverflow.in/11950/compulsory-problem-designer-increase-advantage-locality#c12032

 

2nd one is false.  By increasing associativity we can only reduce "conflict" misses.
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@mcjoshi, multiplex more blocks into a set . suppose, increasing the k set associative to 2k set associative .

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@Kapilp the reference link given above says "On increasing associativity conflict misses increase". How?

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For S1, Increasing line size leads to decrease in number of lines, So, Compulsory misses will be reduced, but Capacity miss will increase. How does it help then??
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ASWER  : (b)

S1: compulsory miss is that which always occur because intialy cache memory is always empty and there is no reference present so first reference will always be a MISS. called compulsory MISS

S2 :this miss will occur when the cache memory size is full due to small size of cache it cannot accommodate all the main memory blocks during the program execution so some of the cache block are discarded and later reterived..so if we increase the associative of the cache than more no of blocks can be hold by cache ..

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Answer: A

compulsory misses can be reduced by increasing cache block/line size.

capacity misses can be reduced by increasing the cache size.

conflict miss can be reduced by increasing the cache associativity.

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