What is cache memory?

It's the area of memory that stores the most-recently accessed data. When a computer needs data once, chances are it will need it again, soon; so computer designers realized they could speed up the computer by storing the most recently accessed data in a high-speed storage area.

Most caches are FIFO (first in, first out). This means that, as the cache fills, the older data is thrown out. This makes sense because you want the most-recently accessed data available. So as data ages, it falls out of the cache to make room for the newer data.
There are several types of cache on your computer:

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Disk cache. Current Windows versions have this, though you can't see it or set it. It reserves an area of RAM to store data that has been accessed from the hard drive. So if the data is requested again from the hard drive, the computer gets it from RAM, which is much faster.

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Hardware cache. Many hard drives have cache. Almost all CD drives have cache; most have 256K or 512K. It speeds up access to the CD and the CD's performance.

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Browser cache. This saves data from recently accessed websites on the hard drive and pulls it off the hard drive if you ask for that information again, instead of taking the time to get it from the Internet. This can really speed up your browsing. Netscape calls it "cache," while Internet Explorer calls it "temporary Internet files."

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Application cache. This type of cache is similar to the others, except it's application specific. For example, Microsoft Word has its own type of cache, but it works much like the others.

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Processor Cache. There are several types:

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Level 1 (L1). Located inside the processor itself, L1 is very fast because the processor doesn't have to go far to get that data. It's usually a small amount because processor real estate is expensive. Intel's first Celeron processor has no cache, but the company gave the Celeron A 128K of internal cache. The Pentium II separates the cache from the main chip but keeps it on the board. This is a disadvantage because the PII cache runs at one-half the processor speed. This is why the Celeron A processor can be faster than a PII, even with less cache.

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Level 2 (L2). L2 cache is usually on the motherboard. Most boards come with 512K L2 cache. Some have a full megabyte. There are faster types of L2 cache that use pipeline burst cache