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In computer science, a cache is a specialized section of a computer's memory that attempts to improve performance by storing information that either has been recently accessed or is expected to be accessed soon. By keeping this information easily accessible, computer performance can be improved immensely. A cache flush is what clears out these sections of memory. Without caches and the ability to flush them, computers would run at significantly slower speeds.
There are various types of caches. A Domain Name System (DNS) cache flush consists of wiping the section of computer memory that stores DNS entries. These entries are what translate a domain name, such as www.wisegeek.com, into a numerical Internet Protocol (IP) address that the computer can use to connect to the website.
Another area of the computer that uses cache flushing is the browser cache. Web browsers store a variety of information concerning which websites a user has visited. In some instances, this information might be used to compromise user security by allowing remote users access to their accounts. Most browsers have a feature that will allow the user to initiate a cache flush that can alleviate these issues by deleting this information.
Users who are worried about security also should be aware of the disk cache. Information written to and read from the hard drive is stored in a cache. Malicious users can access this cache to find out what information on the drive was last accessed by the computer. Specifics of how to perform a disk cache flush vary between operating systems.
Perhaps the most important cache of all is the central processing unit (CPU) cache. This is a specialized type of memory that is used by the processor to perform diverse operations quickly and efficiently. The CPU cache is usually several times faster than a computer's random access memory (RAM), though it is significantly smaller in size. For those seeking to find the best performing computers, CPU cache size and speed are important factors.
Other than security, cache flushes have a variety of effects on computer performance. Disk write caching can be used to increase performance on computers that often write information to the hard disk. This form of cache can have a negative impact on performance in home computers, however. If a computer loses power while information is in the write cache, then the information will be lost.