Problems on Set Associative Mapping - 1 Video Lecture | Question Bank for GATE Computer Science Engineering - Computer Science Engineering (CSE)

Ans. Set associative mapping is a cache mapping technique used in computer architecture to determine the location of data in the cache memory. It is a compromise between direct mapping and fully associative mapping. In set associative mapping, the cache is divided into multiple sets, and each set can hold multiple cache lines. Each memory block is mapped to a specific set, and within that set, it can be placed in any of the cache lines.

Ans. Set associative mapping improves cache performance by reducing the number of cache conflicts that occur in direct mapping. In direct mapping, multiple memory blocks may map to the same cache line, causing conflicts and cache misses. Set associative mapping allows multiple cache lines in each set, reducing the chances of conflicts and improving cache hit rates. This leads to faster access times and improved overall system performance.

Ans. The main difference between set associative mapping and fully associative mapping lies in the number of cache lines each set can hold. In set associative mapping, each set can hold multiple cache lines, while in fully associative mapping, each set contains only one cache line. This means that set associative mapping offers a compromise between direct mapping (limited associativity) and fully associative mapping (maximum associativity).

Ans. The cache index in set associative mapping is calculated using a hash function. The hash function takes the memory block address as input and produces an index value, which is used to determine the set in which the block will be placed. The hash function ensures a uniform distribution of memory blocks across the cache sets, reducing the chances of conflicts and improving cache performance.

Ans. Set associative mapping offers a balance between direct mapping and fully associative mapping, but it also has some trade-offs. One trade-off is the increased complexity of the cache design compared to direct mapping. Set associative mapping requires additional hardware to handle the multiple sets and cache lines. Another trade-off is the potential for increased cache access time compared to fully associative mapping. With set associative mapping, the cache must search multiple locations within a set to find the desired data, which can result in longer access times compared to fully associative mapping. However, these trade-offs are usually outweighed by the improved cache performance achieved through reduced conflicts and improved hit rates.