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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.
However, with a multiple-level cache, if the computer misses the cache closest to the processor (level-one cache or L1) it will then search through the next-closest level(s) of cache and go to main memory only if these methods fail. The general trend is to keep the L1 cache small and at a distance of 1–2 CPU clock cycles from the processor ...
Consider the case when L2 is exclusive of L1. Suppose there is a processor read request for block X. If the block is found in L1 cache, then the data is read from L1 cache and returned to the processor. If the block is not found in the L1 cache, but present in the L2 cache, then the cache block is moved from the L2 cache to the L1 cache.
The resulting load on memory use is known as pressure (respectively register pressure, cache pressure, and (main) memory pressure). Terms for data being missing from a higher level and needing to be fetched from a lower level are, respectively: register spilling (due to register pressure : register to cache), cache miss (cache to main memory ...
The new 192 KB L1 cache in the Lion Cove core acts as a mid-level buffer cache between the L0 data and instruction caches inside the core and the L2 cache outside the core. It is focussed on reducing latency in the event of L0 data cache misses rather than needing to access the L2 cache.
Diagram of a CPU memory cache operation. In computing, a cache (/ k æ ʃ / ⓘ KASH) [1] is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere.
T1, for recent cache entries. T2, for frequent entries, referenced at least twice. B1, ghost entries recently evicted from the T1 cache, but are still tracked. B2, similar ghost entries, but evicted from T2. T1 and B1 together are referred to as L1, a combined history of recent single references. Similarly, L2 is the combination of T2 and B2.
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 ...