From: Andi Kleen <ak@suse.de>
To: Andrew Morton <akpm@osdl.org>
Subject: Re: AMD X2 unsynced TSC fix?
Date: Sat, 28 Oct 2006 02:45:55 -0700
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Cc: thockin@hockin.org, Sergio Monteiro Basto <sergio@sergiomb.no-ip.org>,
       Lee Revell <rlrevell@joe-job.com>, Chris Friesen <cfriesen@nortel.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       john stultz <johnstul@us.ibm.com>
References: <1161969308.27225.120.camel@mindpipe> <20061028063524.GA7669@hockin.org> <20061027234615.791b3942.akpm@osdl.org>
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On Friday 27 October 2006 23:46, Andrew Morton wrote:
> On Fri, 27 Oct 2006 23:35:24 -0700
>
> thockin@hockin.org wrote:
> > On Fri, Oct 27, 2006 at 09:06:12PM -0700, Andi Kleen wrote:
> > > > So far, has I can understand. Seems to me that my computer which have
> > > > a Pentium D (Dual Core) on VIA chipset, also have unsynchronized TSC
> > > > and with the patch of hrtimers on
> > >
> > > Intel systems (except for some large highend systems) have synchronized
> > > TSCs.
> >
> > Does Intel guarantee that, or is that just what we happen to see, so far.
>
> Matthias has a Xeon machine on which the TSCs are unsynced, and which are
> unsyncable - write_tsc() just doesn't do anything.  See thread at
> http://lkml.org/lkml/2006/7/22/104

That is a clear BIOS bug (FSBs are programmed incorrectly) and doesn't seem to 
be common. In fact the BIOS bug is so bad that it's surprising the system
works at all.

-Andi
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