Question

4 blocks, direct-mapped, 1 word per cache line

Reference sequence: 4,8,12,4,8,20,4,888,20,24,12,8,4

Find the number of Compulsory, capacity, and confilict misses.

Also, when It becomes fully associative cache and 2 set-associative cache.

Please explain specifically.

Answer 1

Compulsory miss are first time accesses.

Capacity miss happens due to lack of capacity

Conflict miss happens when there are empty blocks but accessed block is conflicting with already filled block.

Direct Mapped

First reference to block 4 will be compulsory miss as first time accessing.

Remaining all blocks are indexing to block number 0 which is already filled when each address is accessed.

• Compulsory Miss = 1
• Conflict Miss = 12
• Capacity Miss = 0 There is no capacity miss

Fully Associative Cache

In this, blocks will be placed wherever space is available.

As there is only 4 blocks capacity. First 4 blocks will be placed in cache.

• Compulsory misses = 4
• Conflict Misses = 0
• Capacity Misses = 9

There can’t be conflict miss in fully associative cache as blocks are placed based on cache line availability.

2-Way Set Associative Cache

In this, there will be 2 sets each one having 2 blocks

First two blocks will be placed in first set as indexing to set 0.

Remaining block accesses also will index to set 0 so they will cause conflict miss.

• Compulsory misses = 2
• Conflict Misses = 11
• Capacity Misses = 0