Path: utzoo!utgpu!watserv1!watmath!att!occrsh!uokmax!apple!usc!samsung!uunet!mtndew!friedl
From: friedl@mtndew.Tustin.CA.US (Steve Friedl)
Newsgroups: comp.arch
Subject: Re: Workstation Data Integrity
Summary: Memory scrubbing in software
Message-ID: <509@mtndew.Tustin.CA.US>
Date: 9 Sep 90 09:08:36 GMT
References: <2496@crdos1.crd.ge.COM> <1990Sep8.014608.27533@mozart.amd.com> <1990Sep8.172848.4600@amd.com>
Organization: VSI*FAX Tech Ctr, Tustin, CA
Lines: 24

[ discussions on ECC ]

In article <1990Sep8.172848.4600@amd.com>, ching@brahms.amd.com (Mike Ching) writes:
> The problem is that the two errors don't have to occur simultaneously. If
> a soft error is not corrected (by accessing the word and writing a corrected
> word back), a second bit can be corrupted at a later time and result in a
> double bit error when the word is accessed. This is why scrubbing was
> incorporated in DRAM controllers.

On some machines, the scrubbing is done in software.  The newer 3B2s
all have a job running out of cron at the top of the hour that does:

	dd if=/dev/mem of=/dev/null

This seems to serve the same purpose of provoking the single bit errors
in the background so they get fixed right away.

     Steve

-- 
Stephen J. Friedl, KA8CMY / I speak for me only / Tustin, CA / 3B2-kind-of-guy
+1 714 544 6561  / friedl@mtndew.Tustin.CA.US  / {uunet,attmail}!mtndew!friedl

Steve's bright idea #44: COBOL interface library for X Windows