cache

[kash]
noun
1.
a hiding place, especially one in the ground, for ammunition, food, treasures, etc.: She hid her jewelry in a little cache in the cellar.
2.
anything so hidden: The enemy never found our cache of food.
3.
Alaska and Northern Canada. a small shed elevated on poles above the reach of animals and used for storing food, equipment, etc.
verb (used with object), cached, caching.
4.
to put in a cache; conceal; hide.

Origin:
1585–95; < French, noun derivative of cacher to hide < Vulgar Latin *coācticāre to stow away, orig. to pack together, equivalent to Latin coāct(us) collected (past participle of cōgere; see coactive) + -icā- formative v. suffix + -re infinitive ending

cache, cachet, cash.


2. hoard, stockpile, reserve, store. 4. secrete.
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Collins
World English Dictionary
cache (kæʃ)
 
n
1.  a hidden store of provisions, weapons, treasure, etc
2.  the place where such a store is hidden
3.  computing a small high-speed memory that improves computer performance
 
vb
4.  (tr) to store in a cache
 
[C19: from French, from cacher to hide]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

cache
1797, "hiding place," from Fr. Canadian trappers' slang, "hiding place for stores" (1660s), a back formation from Fr. cacher "to hide, conceal" (13c., O.Fr. cachier), from V.L. *coacticare "store up, collect, compress," freq. of L. coactare "constrain," from coactus pp. of cogere "to collect" (see
cogent). Sense extended by 1830s to "anything stored in a hiding place."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
cache   (kāsh)  Pronunciation Key 
An area of computer memory devoted to the high-speed retrieval of frequently used or requested data.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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FOLDOC
Computing Dictionary

cache definition

memory management
/kash/ A small fast memory holding recently accessed data, designed to speed up subsequent access to the same data. Most often applied to processor-memory access but also used for a local copy of data accessible over a network etc.
When data is read from, or written to, main memory a copy is also saved in the cache, along with the associated main memory address. The cache monitors addresses of subsequent reads to see if the required data is already in the cache. If it is (a cache hit) then it is returned immediately and the main memory read is aborted (or not started). If the data is not cached (a cache miss) then it is fetched from main memory and also saved in the cache.
The cache is built from faster memory chips than main memory so a cache hit takes much less time to complete than a normal memory access. The cache may be located on the same integrated circuit as the CPU, in order to further reduce the access time. In this case it is often known as primary cache since there may be a larger, slower secondary cache outside the CPU chip.
The most important characteristic of a cache is its hit rate - the fraction of all memory accesses which are satisfied from the cache. This in turn depends on the cache design but mostly on its size relative to the main memory. The size is limited by the cost of fast memory chips.
The hit rate also depends on the access pattern of the particular program being run (the sequence of addresses being read and written). Caches rely on two properties of the access patterns of most programs: temporal locality - if something is accessed once, it is likely to be accessed again soon, and spatial locality - if one memory location is accessed then nearby memory locations are also likely to be accessed. In order to exploit spatial locality, caches often operate on several words at a time, a "cache line" or "cache block". Main memory reads and writes are whole cache lines.
When the processor wants to write to main memory, the data is first written to the cache on the assumption that the processor will probably read it again soon. Various different policies are used. In a write-through cache, data is written to main memory at the same time as it is cached. In a write-back cache it is only written to main memory when it is forced out of the cache.
If all accesses were writes then, with a write-through policy, every write to the cache would necessitate a main memory write, thus slowing the system down to main memory speed. However, statistically, most accesses are reads and most of these will be satisfied from the cache. Write-through is simpler than write-back because an entry that is to be replaced can just be overwritten in the cache as it will already have been copied to main memory whereas write-back requires the cache to initiate a main memory write of the flushed entry followed (for a processor read) by a main memory read. However, write-back is more efficient because an entry may be written many times in the cache without a main memory access.
When the cache is full and it is desired to cache another line of data then a cache entry is selected to be written back to main memory or "flushed". The new line is then put in its place. Which entry is chosen to be flushed is determined by a "replacement algorithm".
Some processors have separate instruction and data caches. Both can be active at the same time, allowing an instruction fetch to overlap with a data read or write. This separation also avoids the possibility of bad cache conflict between say the instructions in a loop and some data in an array which is accessed by that loop.
See also direct mapped cache, fully associative cache, sector mapping, set associative cache.
(1997-06-25)
The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
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Example sentences
The cache of survival rations was found in a previously forgotten storeroom .
Readers will reach the last page wishing for a secret cache of sequels.
It was a strategy that netted not only a cache of home electronics but five
  cars.
Finding a secret cache of chemical weapons would be perfect.
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