What is cache memory and what are the types and where are they located?

Answer 1

Best Answer - Chosen by Voters

go on this site, read click next
and move on

Source(s):

http://computer.howstuffworks.com/cache.…

Answer 2

google cache and go to wikipedia or similar for answer

Answer 3

a type of memory

Source(s):

2nd amendment for ever

Answer 4

A cache is a block of memory for temporary storage of data likely to be used again. The CPU and hard drive frequently use a cache, as do web browsers and web servers.

A cache is made up of a pool of entries. Each entry has a datum (a nugget of data) which is a copy of the datum in some backing store. Each entry also has a tag, which specifies the identity of the datum in the backing store of which the entry is a copy.

When the cache client (a CPU, web browser, operating system) wishes to access a datum presumably in the backing store, it first checks the cache. If an entry can be found with a tag matching that of the desired datum, the datum in the entry is used instead. This situation is known as a cache hit. So, for example, a web browser program might check its local cache on disk to see if it has a local copy of the contents of a web page at a particular URL. In this example, the URL is the tag, and the contents of the web page is the datum. The percentage of accesses that result in cache hits is known as the hit rate or hit ratio of the cache.

The alternative situation, when the cache is consulted and found not to contain a datum with the desired tag, is known as a cache miss. The previously uncached datum fetched from the backing store during miss handling is usually copied into the cache, ready for the next access.

During a cache miss, the CPU usually ejects some other entry in order to make room for the previously uncached datum. The heuristic used to select the entry to eject is known as the replacement policy. One popular replacement policy, least recently used (LRU), replaces the least recently used entry (see cache algorithms). More efficient caches compute use frequency against the size of the stored contents, as well as the latencies and throughputs for both the cache and the backing store. While this works well for larger amounts of data, long latencies, and slow throughputs, such as experienced with a hard drive and the Internet, it's not efficient to use this for cached main memory (RAM).[citation needed]

When a datum is written to the cache, it must at some point be written to the backing store as well. The timing of this write is controlled by what is known as the write policy.

In a write-through cache, every write to the cache causes a synchronous write to the backing store.

Alternatively, in a write-back (or write-behind) cache, writes are not immediately mirrored to the store. Instead, the cache tracks which of its locations have been written over (these locations are marked dirty). The data in these locations is written back to the backing store when those data are evicted from the cache, an effect referred to as a lazy write. For this reason, a read miss in a write-back cache (which requires a block to be replaced by another) will often require two memory accesses to service: one to retrieve the needed datum, and one to write replaced data from the cache to the store.

Data write-back may be triggered by other policies as well. The client may make many changes to a datum in the cache, and then explicitly notify the cache to write back the datum.

No-write allocation is a cache policy where only processor reads are cached, thus avoiding the need for write-back or write-through when the old value of the datum was absent from the cache prior to the write.

The data in the backing store may be changed by entities other than the cache, in which case the copy in the cache may become out-of-date or stale. Alternatively, when the client updates the data in the cache, copies of that data in other caches will become stale. Communication protocols between the cache managers which keep the data consistent are known as coherency protocols.

Source(s):

wikipedia

Answer 5

Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.

Cache memory is sometimes described in levels of closeness and accessibility to the microprocessor. An L1 cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) L2 is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip.

In addition to cache memory, one can think of RAM itself as a cache of memory for hard disk storage since all of RAM's contents come from the hard disk initially when you turn your computer on and load the operating system (you are loading it into RAM) and later as you start new applications and access new data. RAM can also contain a special area called a disk cache that contains the data most recently read in from the hard disk.

Answer 6

OOOOOOOHHHHHHH my clubpenguin account told me to change my cach thingy!!!!!!

Answer 7

cache memory is located in the directory of the internet browser.
it contains the 3rd party cookies of the pages u browse

Answer 8

In computer science, a cache (pronounced /kæʃ/) is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch (owing to longer access time) or to compute, compared to the cost of reading the cache. In other words, a cache is a temporary storage area where frequently accessed data can be stored for rapid access. Once the data is stored in the cache, future use can be made by accessing the cached copy rather than re-fetching or recomputing the original data, so that the average access time is shorter.

A cache has proven to be extremely effective in many areas of computing because access patterns in typical computer applications have locality of reference. There are several kinds of locality, but this article primarily deals with data that are accessed close together in time (temporal locality). The data might or might not be located physically close to each other (spatial locality).

There are CPU caches
Disk cache
web cache
other cache

Source(s):

http://en.wikipedia.org/wiki/Cache

Answer 9

most of the time, it has something to do with the hardware.

Answer 10

cache is, to the best of my knowledge (explained by a mate who works in IT) what the computer uses to store short term memory. kind of like the stuff youve got open now. say youve got a song open in winamp, the song will be cached by your computer and once you close winamp, the song will be cleared from the cache.

they are located in your RAM, so i guess the more RAM you have the better.

Answer 11

David N whose answer is above deserves the 10 points - it is excellent.

I would only like to add an analogy. Cache memory is "stuff" that is likely something you will need immedialtely. For example, you are going out to meet a new friend for lunch. You both have cell phones, but yours is in the car.

So what do you do. Well, likely you go over to your computer, look up his/her telephone number and write it on a piece of paper. You then take that piece of paper and put it into your pocket and run out the door to your car.

What you have really done, is to put a piece of data or "stuff" into your cache (in this case called L1 cache) because you will have it immediatly and READILY available. Because you are running a bit late, you just reach into your pocket, and dial the number directly into your cell phone (which could now be looked at as L2 cache), and make the telephone call.

If you kind of play with this concept you will see that the closer and faster a piece of information is both used and available, the closer it is to L1 cache.

Hope this helps a bit

Source(s):

mcse ccnp c++

Answer 12

Cache memory ia a small segment of memory used to hang on to frequently accessed data, so it can be re-accessed at faster speed than from its original source.

A modern processor (CPU) typically contains 2 or 3 levels of cache.
Level 1 - smallest, fastest, seperated for program code and data.
Level 2 - Per core on multi-core CPUs that support this, shared on others
Level 3 - On CPUs with per core level 2 cache, there is often a shared level 3 cache.

Older system may have motherboard cache memory, but the increasing speed and multiplier levels made this obsolete.

Hard disks and CD/DVD drives generally contain a cache memory, though this will tend to act as a read-ahead buffer rather than a cache.


Software caches consist of data retained in system memory.
Windows will extensively cache code and data in "unused" system memory.
Most browsers will cache recently accessed page content, to system memory or hard disk.


To go back to where they are located:

CPU cache - on the CPU, occupying a sizable amount of the die space.
Older motherboard cache - RAM chips, socketed or surface mount, or on a socketed module.
Other hardware devices - generally a single surface mount RAM chip.

Answer 13

Cache (pronounced cash) memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving overall system speed. The advantage of cache memory is that the CPU does not have to use the motherboard’s system bus for data transfer. Whenever data must be passed through the system bus, the data transfer speed slows to the motherboard’s capability. The CPU can process data much faster by avoiding the bottleneck created by the system bus.

Source(s):

http://www.wisegeek.com/what-is-cache-memory.htm