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Date: Mon, 15 Aug 2011 15:32:49 +0300
From: Andriy Gapon <avg@FreeBSD.org>
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To: Joe Schaefer <joesuf4@gmail.com>
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Cc: freebsd-hackers <freebsd-hackers@FreeBSD.org>
Subject: Re: Clock stalls on Sabertooth 990FX
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on 13/08/2011 20:16 Joe Schaefer said the following:
> Brand new machine with a Phenom II X6 1100T and under chronic load
> the clock will stop running periodically until the machine eventually completely
> freezes.  Note: during these stalls the kernel is still running, the
> machine is still
> mostly responsive, it's just that the clock is frozen in time.
> 
> I've disabled Turbo mode in the bios and toyed with just about every
> other setting but nothing seems to resolve this problem.  Based on the behavior
> of the machine (just making buildworld will eventually kill it, upping
> the -j flag
> just kills it faster), I'm guessing it has something to do with the
> Digi+ VRM features
> but again nothing I've tried modifying in the bios seems to help.
> 
> I've tried both 8.2-RELEASE and FreeBSD 9 (head).  Running head now with
> a dtrace enabled kernel.
> 
> Suggestions?

On head, start with checking what source is used for driving clocks:
sysctl kern.eventtimer

When the problem starts using vmstat -i to check interrupt rates and see if any
relevant counter gets stuck.

-- 
Andriy Gapon