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From: town@-a.spk.hp.com (Brian R. Town)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Memory Parity. Is It Really Needed
Message-ID: <6040015@-a.spk.hp.com>
Date: 10 Apr 91 18:07:28 GMT
References: <steveh.669386099@tasman>
Organization: Hewlett Packard Company, Spokane, Wa.
Lines: 26

achilles@unixland.uucp (David Holland) writes: 
 
> However, wouldn't the memory test that your computer does when you turn it 
>on or do a "cold" reboot detect memory failures? If so, adding an extra chip 
>for parity not only wastes silicon, board space, money, power, and 
>everything else, but also DECREASES reliability - if the chance of any 
>particular memory chip failing is 1/10,000, the chance of any one of your 
>memory chips failing is 8/10,000 without parity, or 9/10,000 with... 
> 
> ------------
> David A. Holland

This is only true for 'hard' memory failures.  The ones that are going to hurt
you the most are the intermittent ones.  These are the ones that show up once
in a while.  Examples:  A poor connection or joint which is influenced by heat
                        and/or vibrations.  An electrical problem within a
                        memory or support chip which causes the device to have
                        an output signal which is compromized (weak for ex.).
                        This may only show up as an error under certain heat
                        conditons.

Boy, I sure would love to have the 'decresed reliability' of error correcting
memory (you use 12 bits for every byte with it).   ;) ;)

Brian (rather have mem fail 12.5% more often, but always know it did) Town