On the other hand, there is no such effect in the cache hit ratio in the case of a fully associative cache even if the processor has to access the same locations in the memory from two distinct memory pages repeatedly. In a direct mapped cache, there is a significant decrease in the cache hit ratio experienced when it is needed by the processor to access the same locations in the memory from two distinct memory pages repeatedly. On the other hand, in a fully associative cache, the main memory block is mapped with any of the available blocks of the cache. This is because a fixed formula is used in its mapping. In a direct mapped cache, there can be only one possible location for every block in the cache organization from the main memory. On the other hand, in a fully associative cache, the main memory address is divided into Tag and Word fields. The Block and the Word together make the Index. In a direct mapped cache, there are three particular fields in which the memory address is divided into, namely, Tag, Block, and Word. In other words, the cache control logic needs to look at every tag of the block in order to find a match and also find out whether or not a block is in the cache at the same time. On the other hand, in a fully associative cache, it needs comparison with every tag bit to find a match. In a direct mapped cache, there is only one comparison required by using a direct formula to find the effective cache address for mapping. On the other hand, in a fully associative cache, each block of the main memory is loaded into any available line of cache. In simple terms, a direct mapped cache is that where each block of the main memory is mapped into only one particular cache line possible. Conclusion Direct Mapped Cache vs a Fully Associative Cache – The 13 Differences. Which One is Better to Use – Direct Mapped Cache or Fully Associative Cache?.Direct Mapped Cache vs a Fully Associative Cache – The 13 Differences.
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