From owner-freebsd-questions@FreeBSD.ORG  Tue Oct  1 00:32:54 2013
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115])
 (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTP id 316F149C
 for <freebsd-questions@freebsd.org>; Tue,  1 Oct 2013 00:32:54 +0000 (UTC)
 (envelope-from freebsd-questions@m.gmane.org)
Received: from plane.gmane.org (plane.gmane.org [80.91.229.3])
 (using TLSv1 with cipher AES256-SHA (256/256 bits))
 (No client certificate requested)
 by mx1.freebsd.org (Postfix) with ESMTPS id E33482FBC
 for <freebsd-questions@freebsd.org>; Tue,  1 Oct 2013 00:32:53 +0000 (UTC)
Received: from list by plane.gmane.org with local (Exim 4.69)
 (envelope-from <freebsd-questions@m.gmane.org>) id 1VQntT-0006Jq-L6
 for freebsd-questions@freebsd.org; Tue, 01 Oct 2013 02:32:51 +0200
Received: from pool-173-79-84-117.washdc.fios.verizon.net ([173.79.84.117])
 by main.gmane.org with esmtp (Gmexim 0.1 (Debian))
 id 1AlnuQ-0007hv-00
 for <freebsd-questions@freebsd.org>; Tue, 01 Oct 2013 02:32:51 +0200
Received: from nightrecon by pool-173-79-84-117.washdc.fios.verizon.net with
 local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00
 for <freebsd-questions@freebsd.org>; Tue, 01 Oct 2013 02:32:51 +0200
X-Injected-Via-Gmane: http://gmane.org/
To: freebsd-questions@freebsd.org
From: Michael Powell <nightrecon@hotmail.com>
Subject: Re:  cause of reboot
Date: Mon, 30 Sep 2013 20:32:39 -0400
Lines: 24
Message-ID: <l2d56v$svs$1@ger.gmane.org>
References: <519911380551058@web20j.yandex.ru>
 <20130930190944.281aa46d@davenulle.org> <l2cg1g$oqj$1@ger.gmane.org>
 <20131001000739.GC68360@neutralgood.org>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7Bit
X-Complaints-To: usenet@ger.gmane.org
X-Gmane-NNTP-Posting-Host: pool-173-79-84-117.washdc.fios.verizon.net
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
Reply-To: nightrecon@hotmail.com
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
 <mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 01 Oct 2013 00:32:54 -0000

kpneal@pobox.com wrote:
[snip]
> While we're throwing ideas onto the table let me mention power supplies.
> Power supplies and hard drives are in a race to see which one will fail
> first. It may be that the power supply is marginal and added load from
> the drives being hit hard may send it over the edge. How heavily loaded
> is the machine in question?

Absolute and total agreement with this. As they age and the filter caps leak 
and dry out more it will eventually become apparent. But in the meantime the 
output DC can just about meet spec up until really loaded. Then the ripple 
becomes so excessive it's not quite "DC" any longer. You can clearly see it 
using an oscilloscope. 

The 0300 AM periodic does hammer a machine enough to possibly push a 
marginal power supply over the edge. I once had a box where the RAM chips 
would "sing" with a high-pitched whistle only during the 0300 periodic run. 
It sounded just like the horizontal output on a television right before 
destruction.  :-) 
 
[snip]

-Mike