Learn about the technologies behind the Internet with The TCP/IP Guide!
NOTE: Using robot software to mass-download the site degrades the server and is prohibited. See here for more.
Find The PC Guide helpful? Please consider a donation to The PC Guide Tip Jar. Visa/MC/Paypal accepted.
View over 750 of my fine art photos any time for free at DesktopScenes.com!

[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Construction and Operation of the Hard Disk ]

Hard Disk Cache and Cache Circuitry

All modern hard disks contain an integrated cache, also often called a buffer. The purpose of this cache is not dissimilar to other caches used in the PC, even though it is not normally thought of as part of the regular PC cache hierarchy. The function of cache is to act as a buffer between a relatively fast device and a relatively slow one. For hard disks, the cache is used to hold the results of recent reads from the disk, and also to "pre-fetch" information that is likely to be requested in the near future, for example, the sector or sectors immediately after the one just requested.

The use of cache improves performance of any hard disk, by reducing the number of physical accesses to the disk on repeated reads and allowing data to stream from the disk uninterrupted when the bus is busy. Most modern hard disks have between 512 KiB and 2 MiB of internal cache memory, although some high-performance SCSI drives have as much as 16 MiB, more than many whole PCs have!

Note: When someone speaks generically about a "disk cache", they are usually not referring to this small memory area inside the hard disk, but rather to a cache of system memory set aside to buffer accesses to the disk system.

Next: Cache Circuitry and Operation


Home  -  Search  -  Topics  -  Up

The PC Guide (http://www.PCGuide.com)
Site Version: 2.2.0 - Version Date: April 17, 2001
Copyright 1997-2004 Charles M. Kozierok. All Rights Reserved.

Not responsible for any loss resulting from the use of this site.
Please read the Site Guide before using this material.
Custom Search