Memory Cache

Random Access Memory (RAM) moves the data from the memory storage devices (e.g., harddrive, floppy disk,CD-ROM, tape drive) to the microprocessor(s). The faster the refresh rate the faster the data is moved. A refresh rate is the speed at which the electrical charges in the capacitors are refreshed. One way that information processing is speeded up is through the use of memory cache.

Memory cache is a special area of computer memory into which the computer transfers data needed from the disk storage area of the computer. This reduces the time it take for the Central Processing Unit (CPU) to retrieve data from the main memory and speeds up the information processing of the computer. The greater the cache, the faster the processing speed.

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The hard drive gets information faster than any other device on the computer. If the CPU needs data, it is the disk cache, not the hard drive that it goes to first. The cache is part of the computer's main memory and it's job is to speed up data transfer while the hard drive basically stores the information.

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The speed of the chips used in the cache and the algorithm the cache uses to determine which data to store in the cache are the two main factors in determining the effectiveness of the memory cache. If the algorithm is really good at guessing what data will be requested next, then the cache will come up with a hit more often.

As more data is requested by your software, the cache replaces the data in the highspeed chips the longest with the new data. The memory cache is following the "First In, First Out Rule." The principal of the rule is that the data that has been hanging around the longest is the least likely to be requested by the software next.

The Basic Process:

The computer asks for data stored on disk. The cache manager retrieves the data and sends it to main memory. The cache manager reads additional data from the disk and transfers it to cache. When more data is requested by the computer, the manager checks the cache first to see if it is there. If so, then it is sent to the main memory, speeding up the processing speedl. If the data is not in cache, then the cache manager must locate the dat on disk, slowing down the processing time.

Note: If the processor does not have the cache, it may sit at idle for several clock cycles (shortest time during which any operation can happen in a computer) until the requested data is sent to it from the memory storage device.

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• Main Memory (RAM) Slowest: This cache places a copy of data from the main memory in cache so that it contains the data most recently used by the CPU. It is accessed if internal and external cache is not available.

Internal Cache (Primary Cache) Fastest: This cache consists of a memory chip built into the CPU. It is the fastest way for the computer to get data information. This is where the computer looks first to find data. It stores a small amount of the most recent data used by the central processing unit. External Cache (Secondary Cache) Second Fastest: This cache is found on the motherboard and is made up of SRAM chips. The CPU first looks in external cache and if it cannot find the information then it goes to the external cache. This cache also stores information most recently used by the central processing unit.

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For the more advanced user click here to learn how to maintain your memory cache.

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