Cache Memory

Cache memoryCache memory is a high-speed random access memory used by a computer's CPU for temporary storage of information. It increases productivity, because it stores the most frequently used data and instructions "closer" to the processor, where the CPU can quickly get it.Cache memory directly affects the speed of calculations and helps the CPU to work with more balanced load. Imagine an array of information used at your office. Small amounts of information needed in the first place, say a list of subdivisions phones, hang on the wall above your desk. Similarly, you keep at hand the information on current projects. Less frequently used reference books, for example, a local telephone directory, are shelved next to the your desk. All the literature you use very seldom takes up the shelves of the bookcase.Computers store data according to a similar hierarchy. When an application starts, the data and commands are transferred from a slow hard drive to random access memory (Dynamic Random Access Memory, or DRAM), where the processor can quickly get them. RAM serves as a cache memory for the hard drive.Although RAM is much faster than the hard drive, however, it does not keep pace with the needs of the processor either. Therefore the data required is often transmitted to the next level of fast memory, called cache memory of the second level. It may be located in a separate high-speed chip of static RAM (SRAM), installed in the immediate vicinity of the CPU (new processors has second level cache memory integrated directly into the processor chip).At a higher level information that is used more often (say, commands in multiple loops), is stored in a special section of the processor, called the cache memory of the first level. This is the fastest memory.When the processor is to execute a command, it analyzes the state of its data registers at first. If the required data isn't located in registers, it addresses to the cache memory of the first level, and then to the cache memory of the second level. If the data is not stored in any of the cache memory types, the processor accesses RAM. And only if the necessary data is not there, it reads data from your hard drive.If the processor detects data in one of the types of cache memory, it is called a "hit"; the failure is called a "miss". Every miss entails a delay, as the processor will attempt to detect the data at another cache level, which takes up a lower place in the hierarchy. In well-engineered systems with software algorithms, which perform prefetch of data before it is required, the percentage of "hits" can reach 90.

Category:

Science & Technology

Tags:

• data bus
• data transfer
• HDD
• memory
• microprocessor
• PC

[MrWorldWide81z]

hell with this video.:|