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From: frazier@oahu.cs.ucla.edu (Greg Frazier)
Newsgroups: comp.arch
Subject: Re: Parity (was: Time between memory failure)
Message-ID: <31673@shemp.CS.UCLA.EDU>
Date: 8 Feb 90 17:25:35 GMT
References: <1911@sunquest.UUCP> <38420@apple.Apple.COM> <2102@crdos1.crd.ge.COM>
Sender: news@CS.UCLA.EDU
Reply-To: frazier@oahu.UUCP (Greg Frazier)
Organization: UCLA Computer Science Department
Lines: 27

In article <2102@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.com (bill davidsen) writes:
+In article <38420@apple.Apple.COM> baum@apple.UUCP (Allen Baum) writes:
+
+| Actually, especially when it comes to PCs, parity migh be a loss rather
+| than a win, but not for the reasons you'd suspect. Often, it's the parity
+| generating circuitry that's the critical path, and it fails more often than
+| the memories. Thus, you get lots of parity errors that aren't really errors.
+| Its the parity checking and generating circuitry that's the weak point.
+
+  I can't say you're wrong about that because I don't have the detailed
+stats on all the computers in the world, but I did ask one of the repair
+guys here about memory vs. parity circuit failures, and he said it was
+memory virtually all the time. They maintain at least 800 machines which
+are PCs or PC clones with parity checking.

Correct me if I'm wrong, but aren't we talking about soft
errors, here?  If so, the repair man isn't going to see
them.  I would be a bit surprised if parity hardware experienced
more soft errors than memory, but I'd be shocked if parity
hardware had more hard errors.

Greg Frazier
..................................................................
"They thought to use and shame me but I win out by nature, because a true
freak cannot be made.  A true freak must be born." - Geek Love

Greg Frazier	frazier@CS.UCLA.EDU	!{ucbvax,rutgers}!ucla-cs!frazier