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Date: Mon, 24 May 2010 13:20:45 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: john stultz <johnstul@us.ibm.com>
CC: Dan Magenheimer <dan.magenheimer@oracle.com>,
       Brian Bloniarz <bmb@athenacr.com>, Ingo Molnar <mingo@elte.hu>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>, Andi Kleen <andi@firstfloor.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Venkatesh Pallipadi <venki@google.com>, chris.mason@oracle.com,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: Export tsc related information in sysfs
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On 05/24/2010 11:51 AM, john stultz wrote:
> 
> Hmmm. That could be an option for newer cpus that I wouldn't oppose.
> 
> While Peter is correct that the stamped value is probably not very
> accurate, atleast it would be constant from boot to boot, and NTP's
> calculated drift value would be correct. 
> 
> We'd need a check to make sure its not way off, since NTP will give up
> if its outside 500ppm.  So as long as its close to the calibrated value,
> we probably could use it.
> 

Is that still the case?  I thought newer versions of NTP could deal with
large values.  Inaccuracies of way more than 500 ppm are everyday.

	-hpa