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Cache hierarchy, or multi-level cache, is a memory architecture that uses a hierarchy of memory stores based on varying access speeds to cache data. Highly requested data is cached in high-speed access memory stores, allowing swifter access by central processing unit (CPU) cores.
The number of levels in the memory hierarchy and the performance at each level has increased over time. The type of memory or storage components also change historically. [6] For example, the memory hierarchy of an Intel Haswell Mobile [7] processor circa 2013 is: Processor registers – the fastest possible access (usually 1 CPU cycle). A few ...
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. [1] A cache is a smaller, faster memory, located closer to a processor core, which stores copies of the data from frequently used main memory locations.
These cache hits and misses contribute to the term average access time (AAT) also known as AMAT (average memory access time), which, as the name suggests, is the average time it takes to access the memory. This is one major metric for cache performance measurement, because this number becomes highly significant and critical as processor speed ...
For this reason, a read miss in a write-back cache may require two memory accesses to the backing store: one to write back the dirty data, and one to retrieve the requested data. Other policies may also trigger data write-back. The client may make many changes to data in the cache, and then explicitly notify the cache to write back the data.
A cache coherence protocol is used to maintain cache coherency. The two main types are snooping and directory-based protocols. Cache coherence is of particular relevance in multiprocessing systems, where each CPU may have its own local cache of a shared memory resource. Coherent caches: The value in all the caches' copies is the same.
Set-associative cache is a trade-off between direct-mapped cache and fully associative cache. A set-associative cache can be imagined as a n × m matrix. The cache is divided into ‘n’ sets and each set contains ‘m’ cache lines. A memory block is first mapped onto a set and then placed into any cache line of the set.
Memory organization is an aspect of computer architecture that is concerned with the storage and transfer of data and programs [1]. There are several ways to organise memories with respect to the way they are connected to the cache: one-word-wide memory organisation; wide memory organisation; interleaved memory organisation; independent memory ...