On 30 May 2003, at 13:18, Huonga3TCV wrote:

> What does the word "cache" mean when talk about hardware?

  Computer storage is often arranged in "tiers".  The two best known in
current technology are RAM, which is relatively fast but expensive, and disk
space which is, by comparison, much slower and cheaper.
  But there are other useful points along the speed-vs-cost curve.  Backup
media need to be even cheaper than hard drives, but generally are REALLY
slow, for instance.

  Cache refers to going in the other direction.  In hardware, it generally
refers to a small amount of memory incorporated into the CPU, so that for
recently-used information it doesn't have to spend time going out to RAM to
retrieve it again.  (Believe it or not, fetching values from RAM is a
relatively slow operation for the CPU.  Writing them back is even worse --
some of the cache may hold values that are waiting to be written back to RAM
by a module within the CPU while the "processor" piece moves on to other
steps of the program.)

David Gillett

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