[ntp:questions] Re: SUSE OSS 10 NTPD Clock Drift

Richard B. Gilbert rgilbert88 at comcast.net
Fri Jan 20 12:52:39 UTC 2006

David J Taylor wrote:

>Richard B. Gilbert wrote:
>>WinDoze exhibits the same problem with lost clock interrupts.  The
>>difference is that there is nothing you can do about WinDoze except
>>run a better O/S!  The problem results from interrupts being masked or
>>disabled for two or more consecutive clock "ticks".   Only the first
>>"tick" registers, the rest are lost.  This typically happens during
>>heavy disk activity.  Runing the multi-media timers can also gum
>>things up royally but there is a fix or workaround for that.  If your
>>clock gains rather than loses time, you needn't worry about lost
>>interrupts. If the machine drifts badly when idle, the problem is
>>probably not lost interrupts.
>What is your evidence for saying this about lost interrupts with Windows? 
>I ask because I have Windows running NTP on a number of systems ranging 
>from an old 266MHz AMD running Windows NT4 up to a 2.8GHz Pentium 4 
>running Windows 2000, and a 1.9GHz Pentium 4 running Windows XP, and I 
>have not seen problems with lost interrupts.  Of course, disk DMA should 
>be enabled, and I suppose that a badly written third-party device driver 
>could cause problems.  What situations might cause lost interrupts, and 
>how can they be avoided?  Do you think these problems are present in the 
>basic OS?
>You are, of course, correct that the multi-media timers do need to be 
>permanently enabled (if you run software which might enable and disable 
>them), and fortunately there is now a version of NTP which does that:
>  http://www.meinberg.de/english/sw/ntp.htm
My words were based on what I've read here.  I do not run ntpd on 
Windoze.   Based on about twelve years as a Windoze user from 3.1 to XP, 
I think it's fair to say that Windoze is badly written.  It has gotten 
better over the years but it's still far from what I'd call reliable, 
well designed, or well executed.  My Unix and VMS systems stay up as 
long as the power stays on (I've had a VMS system with over two years of 
continuous up time); my Windows systems have to rebooted after a week to 
ten days of use (it used to be daily, or more)!

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