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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.
A two-level adaptive predictor remembers the history of the last n occurrences of the branch and uses one saturating counter for each of the possible 2 n history patterns. This method is illustrated in figure 3. Consider the example of n = 2. This means that the last two occurrences of the branch are stored in a two-bit shift register.
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.
Unlike the RAM machine model, it also introduces a cache: the second level of storage between the RAM and the CPU. The other differences between the two models are listed below. In the cache-oblivious model: The cache on the left holds blocks of size each, for a total of M objects. The external memory on the right is unbounded.
– The cache is set M (D) if the "shared line" is off, otherwise is set O (SD). All the other copies are set S (V) Cache in E (R) or M (D) state (exclusiveness) – The write can take place locally without any other action. The state is set (or remains) M (D) Write Miss – Write Allocate – Read with Intent to Modified operation
Level 2 (L2) Instruction and data (shared) – 1 MiB [citation needed] [original research] in size. Best access speed is around 200 GB/s [9] Level 3 (L3) Shared cache – 6 MiB [citation needed] [original research] in size. Best access speed is around 100 GB/s [9] Level 4 (L4) Shared cache – 128 MiB [citation needed] [original research] in size.
If all blocks in the higher level cache are also present in the lower level cache, then the lower level cache is said to be inclusive of the higher level cache. If the lower level cache contains only blocks that are not present in the higher level cache, then the lower level cache is said to be exclusive of the higher level cache. If the ...
Cache hits are the number of accesses to the cache that actually find that data in the cache, and cache misses are those accesses that don't find the block in the cache. 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 ...