Why computers need that Cache?

What if it asks for a book reader that does not exist in the cache (bag)? In this case, the librarian of the cache is less efficient than without the cache, because the librarian takes the time to find a book in his bag. One of the challenges of cache design is to minimize the impact of cache searches, and modern hardware has reduced the time delay to zero.

Even with our librarian example, the latency time (waiting time) is very small compared to the cache search time to go into storage. Cache is small (10 books) and the time required to find only a fraction of the time traveling to the trip.

"Layers" Cache modern PCs have a lot of cache layer. This does not include cache found in some peripherals, such as hard disk for example. Growing up and getting closer to the processor faster than the layer beneath it (see table). Each layer also caches layer below it, because the higher speed. Given the slow processor compared to some of these devices is to avoid accessing the slow use of cache is very important. Cache Level 1 and Level 2 In the microprocessor to access main memory (RAM), it does so in about 60 nanoseconds (billionths of a second seperenampuluh). This time is very fast.

Microprocessors can have 2 nanosecond cycle time, microprocessor 60 nanoseconds seems so very long. What if we make a special memory bank, a small but very fast (about 30 nanoseconds)? This is two times faster than main memory access. This is called a level 2 cache or L2 cache. What if the system memory to make a smaller but faster directly into the micro processor chip? Thus, this memory is not accessible to the processor speed memory bus speed. This is the L1 cache, which on a Pentium 233-megahertz (MHz) 3.5 times faster than the L2 cache, and two times faster than main memory access. Computers have many subsystems. You can put the cache in between them to increase performance.

Here is an example. We have a microprocessor (the fastest in the computer). Then there is the L1 cache caches the L2 cache to main memory cache that can be used (and often used) as a cache for slower devices such as hard disks and CD-ROM. Hard disks are also used to cache the slower medium - your Internet connection. Internet Connection cache subsystem is the slowest link in your computer.

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