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List:       ntp-hackers
Subject:    Re: [ntp:hackers] Any chance of someone looking at bug 1189?
From:       "David J Taylor" <david-taylor () blueyonder ! co ! uk>
Date:       2009-06-10 15:52:01
Message-ID: 73E315B4DD0D4FC4BA4C25C8B7548D9D () narvik
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Dave Hart wrote:
> On Wed, Jun 10, 2009 at 10:05 AM, David J
> Taylor<david-taylor@blueyonder.co.uk> wrote:
>> Any chance of someone looking at bug 1189?
>>
>> 4.2.4 and 4.2.5 appear to have grossly different behaviours on
>> Windows Vista and Windows-7 systems. Some help in resolving this
>> would be appreciated.
>
> Vista and Win7 systems are different than older Windows releases
> because they have a system clock precision around 1 msec (-10).  With
> my private "QPC" binaries built on 4.2.4p6, and with 4.2.5p162 and
> later, the Windows interpolation scheme is disabled on Vista and
> later, and ntpd runs with a precision around -10.  With all official
> 4.2.4 releases on Windows, and with earlier 4.2.5, ntpd performance on
> Vista and later is miserable due to failing interpolation.
[]
> Cheers,
> Dave Hart

Dave,

Thanks for that.  Just to clarify what I'm seeing for those who haven't 
read bug 1189:

On a Windows-7 system with "well-behaved" hardware:

  4.2.4p6 "QPC" - average jitter 1.2ms

  4.2.5p181 - average jitter 9ms

On a Windows Vista SP1 system with "badly-behaved" hardware:

  4.2.4p6 "QPC" - jitter 3ms

  4.2.5p181 - jitter 15ms

[The "badly behaved" hardware is a USB satellite data reception device, 
receiving some 50GB /day.  It appears from the positive spikes in the 
offset graphs that there may be lost interrupts.  It's an unwelcome 
complication in these tests.]

I do hope that someone with the capability of testing using OpenWRT can 
help.

Cheers,
David
-- 
SatSignal software - quality software written to your requirements
Web:  www.satsignal.eu
Email:  davidtaylor@writeme.com 


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