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Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!fortune!wall
From: wall@fortune.UUCP (Jim Wall)
Newsgroups: net.micro
Subject: Re: another *parity* argument
Message-ID: <3987@fortune.UUCP>
Date: Mon, 13-Aug-84 17:39:38 EDT
Article-I.D.: fortune.3987
Posted: Mon Aug 13 17:39:38 1984
Date-Received: Tue, 14-Aug-84 02:14:41 EDT
References: <692@sri-arpa.UUCP>, <1217@vax2.fluke.UUCP>
Organization: Fortune Systems, Redwood City, CA
Lines: 22


   Remember that a parity error is telling you that your memory
cannot be trusted, at all! Memory parity errors are all hard, once
failed, they can never be trusted until rewritten. Usually if one
location is bad then other locations will be as well.

    What most systems do upon a detection of a parity error is 
jump to a ROM based error routine that sends an error message
to the appropriate output device and gracefully brings itself
down. It never tries to recover any data or program. I know people
will scream over this, but you cannot be sure of the memory 
anymore, so trying to save portions of it will just cause grief.

Remember that memory failures are rarely just one address affected,
most are caused by power surges, ESD, and other similar events.

EDC is better, but not at all perfect, and for the cost isn't worth
it in my book. Now fault tolerence is entirely a different story....

					-Jim Wall
					!amd!fortune!wall