[ntp:questions] Performance of NTP under Windows Vista?

Ryan Malayter malayter at gmail.com
Tue Nov 20 14:39:09 UTC 2007

On Nov 19, 12:15 pm, "David J Taylor" <david-tay... at blueyonder.not-
this-bit.nor-this-bit.co.uk> wrote:
> I don't currently understand the behaviour, as it seemed to take several
> days to reduce the offset by a hundred milliseconds (averaged), whilst
> showing a lot of intermediate noise, followed by sudden cessation of the
> noise when the offset was near zero.
> I'd love to hear from anyone who has made comparative performance
> measurements, or who has suggestions as to how to proceed.

My previous reading indicates that Vista and Server 2008 have had
significant changes to their internal timing architecutre, mostly to
better support multi-media and near-real-time applications, as well as
enhanced power management. So I think, perhaps, ntpd might be making
assumptions that no longer apply in the Vista world. I am unsure of
the complete changes, however.

There is also this bug in the Vista driver for the High Precision
Event Timer, which is available on newer hardware:
http://support.microsoft.com/kb/933272. I would test with that patch.

We only have Vista on laptops at the moment, with variable
connectivity and lots of sleep/wake cycles. So we just use the built-
in Windows Time Service, which handles those conditions well enough to
keep things within 100ms or so. Ntpd did not behave well in my
previous tests with various network interfaces coming on and off
(Wired Etherenet, WiFi, and EVDO connections are used intermittently
throughout the day on all of our laptops). Plus power modes changing
all the time.

I will check into deploying ntpd on Vista desktops as soon as we get
one deployed, but we only seem to be deploying laptops these days.

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