Welcome to Linux Knowledge Base and Tutorial
"The place where you learn linux"
International Rescue Committe

 Create an AccountHome | Submit News | Your Account  

Tutorial Menu
Linux Tutorial Home
Table of Contents
Up to --> The Computer Itself

· Memory
· Cache Memory

Man Pages
Linux Topics
Test Your Knowledge

Site Menu
Site Map
Copyright Info
Terms of Use
Privacy Info
Masthead / Impressum
Your Account

Private Messages

News Archive
Submit News
User Articles
Web Links


The Web

Who's Online
There are currently, 63 guest(s) and 0 member(s) that are online.

You are an Anonymous user. You can register for free by clicking here

Linux Tutorial - The Computer Itself - Memory
  AGP ---- RAM  


Memory is the part of the computer where your program and data are while they are being used by the CPU. Contrast this to a hard disk or floppy, where the program is sitting on the disk and is not being used. (Of course with operating systems like Linux, parts of both the program and the data can be stored on the disk, even as the program is running.) There are two types of memory that are most common talked about: RAM and cache.

In most memory today, an extra bit is added for each byte. This is a parity bit. Parity is a simple way of detecting errors within a memory chip (among other things). If an odd number of bits is set, the parity bit will be set to make the total number of bits set an even number (most memory uses even parity). For example, if three bits are set, the parity bit will also be set to make the total bits set four.

When data is written, the number of set bits is calculated and the parity bit is set accordingly. When the data is read, the parity bit is also read. If the total number of bits set is even, all is well. However, if an odd number of data bits is set and the parity bit is not set, or if an even number of data bits is set and the parity bit is set, a parity error has occurred.

When a parity error occurs in memory, the state of the system is uncertain. To prevent any further problems, the parity checking logic generates a Non-maskable Interrupt (NMI), and the CPU immediately jumps to special codes called NMI service routines.

When Linux is interrupted with an NMI as the result of a parity error, it too realizes things are not good, and the system panics. The panic causes the system to stop everything and shut down. Certain machines support ECC (Error Correcting Code) RAM, which corrects parity problems before it kills your system.

 Previous Page
  Back to Top
Table of Contents
Next Page 


Test Your Knowledge

User Comments:

You can only add comments if you are logged in.

Copyright 2002-2009 by James Mohr. Licensed under modified GNU Free Documentation License (Portions of this material originally published by Prentice Hall, Pearson Education, Inc). See here for details. All rights reserved.
Help us cut cost by not downloading the whole site!
Use of automated download sofware ("harvesters") such as wget, httrack, etc. causes the site to quickly exceed its bandwidth limitation and therefore is expressedly prohibited. For more details on this, take a look here



Security Code
Security Code
Type Security Code

Don't have an account yet? You can create one. As a registered user you have some advantages like theme manager, comments configuration and post comments with your name.

Help if you can!

Amazon Wish List

Did You Know?
You can get all the latest Site and Linux news by checking out our news page.


Tell a Friend About Us

Bookmark and Share

Web site powered by PHP-Nuke

Is this information useful? At the very least you can help by spreading the word to your favorite newsgroups, mailing lists and forums.
All logos and trademarks in this site are property of their respective owner. The comments are property of their posters. Articles are the property of their respective owners. Unless otherwise stated in the body of the article, article content (C) 1994-2013 by James Mohr. All rights reserved. The stylized page/paper, as well as the terms "The Linux Tutorial", "The Linux Server Tutorial", "The Linux Knowledge Base and Tutorial" and "The place where you learn Linux" are service marks of James Mohr. All rights reserved.
The Linux Knowledge Base and Tutorial may contain links to sites on the Internet, which are owned and operated by third parties. The Linux Tutorial is not responsible for the content of any such third-party site. By viewing/utilizing this web site, you have agreed to our disclaimer, terms of use and privacy policy. Use of automated download software ("harvesters") such as wget, httrack, etc. causes the site to quickly exceed its bandwidth limitation and are therefore expressly prohibited. For more details on this, take a look here

PHP-Nuke Copyright © 2004 by Francisco Burzi. This is free software, and you may redistribute it under the GPL. PHP-Nuke comes with absolutely no warranty, for details, see the license.
Page Generation: 0.07 Seconds