Why cache memory

Cache memory Cache memory is a type of high-speed random access memory RAM which is built into the processor. To get around this issue, different types of cache exist: L1 cache has extremely fast transfer rates, but is very small in size. The processor uses L1 cache to hold the most frequently used instructions and data. L2 cache is bigger in capacity than L1 cache, but slower in speed.

In this case, the cache consists of a number of sets, each of which consists of a number of lines. The correspondence between the main memory blocks and those in the cache is specified by a mapping function. Types of Cache — Primary Cache — A primary cache is always located on the processor chip.

This cache is small and its access time is comparable to that of processor registers. Secondary Cache — Secondary cache is placed between the primary cache and the rest of the memory.

It is referred to as the level 2 L2 cache. Often, the Level 2 cache is also housed on the processor chip. Locality of reference — Since size of cache memory is less as compared to main memory.

So to check which part of main memory should be given priority and loaded in cache is decided based on locality of reference. Types of Locality of reference Spatial Locality of reference This says that there is a chance that element will be present in the close proximity to the reference point and next time if again searched then more close proximity to the point of reference.

Temporal Locality of reference In this Least recently used algorithm will be used. The processor sends bit addresses to the cache controller. Each cache tag directory entry contains, in addition, to address tag, 2 valid bits, 1 modified bit and 1 replacement bit.

The processor generates bit addresses. The cache controller maintains the tag information for each cache block comprising of the following. What is the total size of memory needed at the cache controller to store meta-data tags for the cache? Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Skip to content. Change Language.

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