Final answer:
The statement is true: in a set-associative cache, a block can be placed in a fixed number of locations within a set, and a cache allowing placement in n locations is called an n-way set-associative cache. This configuration is a compromise between direct-mapped and fully associative caches, aiming to optimize cache performance.
Step-by-step explanation:
The statement is true. In a set-associative cache, each block can indeed be placed in a fixed number of locations. A set-associative cache that allows a block to be placed in n locations is known as an n-way set-associative cache. This means that the cache is divided into sets, and each set can hold n different blocks. Blocks are mapped to a specific set, but can be placed in any valid location within that set. This configuration aims to reduce the chance of collisions, where multiple blocks compete for the same cache location, hence improving cache performance compared to a direct-mapped cache.
In contrast to a direct-mapped cache, where each block from the main memory maps to exactly one cache line, and a fully associative cache, where a block can go in any cache line, set-associative cache represents a middle ground. In a 4-way set-associative cache, for instance, the cache is divided into sets of 4 lines each, and a block can be placed in any one of these four lines. The cache set to which a block belongs is determined by its address.
When the processor needs to retrieve data, it will look in the cache set determined by the address of the data it requires. If the data is found within the set (a cache hit), processing can continue quickly. If the data is not found (a cache miss), the processor must fetch the data from the main memory, and it will decide which of the n locations the new block will replace based on a cache replacement policy such as Least Recently Used (LRU).