There are different kinds of caches in a computer, but basically they all have the same utility, to speed things up. The most common is the CPU cache. Nowadays all microprocessors have quite a few built-in cache chips and the main difference between each other is the size of them.
Basically, a cache is a place where some data is stored for further use. For example the browser cache will store some parts or copies of the web pages you visit in a period of time and this way it will be much faster to load next time. CPU cache is a little more complicated than that and it is not just one cache, it has different modules of L1 and L2 caches.
CPU cache is basically a memory bank to link the CPU and the main memory. The main function is that this cache is much faster than the main memory bank and thus, the instructions can be executed at a higher speed and data can be written and read much faster too. The mechanic of this is that the memory sends some data blocks to the cache (called cache lines) and the data is written and read in the cache instead of the main memory.
CPU cache benefits of what is called temporal locality. This means that if a data is going to be used more than once it is much faster if it is localized in the cache to be available next time than if the system has to access the memory bank each time it needs the data. Another benefit is that data is usually stored sequentially and as the data is sent in cache lines so the next instruction may also be in the cache and this is called a “cache hit” on the other hand if the next instruction is not allocated in the cache and the processor has to go to the memory to get the data, this is called a “cache miss”. Of course the more cache hits the faster the data will be processed.
Another cache is the disk cache. This is a special cache only for disk units and it is located in the disk controller board. The function of this cache is to bridge the CPU and the disk the same way as the CPU cache bridges the CPU and the memory. The function of this cache is exactly the same as the CPU cache, to save time. When the processor needs information from a disk unit, instead of copying the needed data a larger block is copied to the disk cache and keeps stored there some time. If further reads need data from the same disk, the data may be there and then it won’t be necessary another access to disk which is much slower than accessing to the cache. This cache can be also used for writing and then the data is stored in the cache “waiting” to be written to the disk when the processor is idle and this way the processor time use is improved.
