L1 Cache

What is L1 Cache?

L1 Cache refers to level 1 cache or internal cache. It is a memory bank built in the processor core used for storing information recently accessed by a processor. It is also referred to as the primary cache as it is the cache closest to the processor.

Function

Caching lies in a principle in computer science called locality of reference. This principle declares that when a processor is referred to a certain location in its memory, it is most likely that the processor would refer to it again in the near future. Employing a cache to store recently accessed memory values keeps the processor from going to the memory each time it is asked to reload them. This results in a considerable boost in its performance as a computer’s main memory is often slower than the processor’s cache.

L1 cache speeds up the access of recently accessed information by first checking if the memory data requested by the processor is already loaded in the cache. The cache controller on the chip performs this function with the use of special circuitry. If the requested memory value is already loaded in the cache, the system is spared the time it would take to retrieve the information from the main memory.

Organization of L1 Cache

There are generally two ways in which a processor can organize its L1 cache:

  1. Some processors utilize a unified or integrated cache, which is a single cache used to hold both microprocessor instructions and program data.
  2. Other processors split their L1 cache into two caches of equal size. One cache is used to hold program data, whilst the other is used to hold microprocessor instructions.

Nonetheless, there is no significant difference in the overall performance of either the unified and separate cache.

Specifications

The typical size of an L1 cache ranges from 8kb to 64kb. Newer processors have larger amounts, whilst older processors have no primary cache at all.

L1 caches are the fastest memory in the computer as they run at the speed of the processor and they are incorporated in it. They are also often set associative to improve the chances of getting a hit on the cache.