[ntp:questions] Win7: ntpd adjusting time backwards

David Taylor david-taylor at blueyonder.co.uk.invalid
Sun Dec 9 16:00:15 UTC 2012

On 09/12/2012 15:00, Jeroen Mostert wrote:
> No, the service is definitely running continuously.
> Fair enough. I have no problem not getting a File -> Open menu from the
> likes of gnuplot, but that's because that *only* has a command-line
> interface so I expect no better. If something starts up with a GUI,
> though, I expect to be able to use it without reading documentation.
> Funny how that goes. :-)
> Provided it is named "peerstats.somethingsomething", right?
> Unfortunately, the easy-to-find pages for troubleshooting NTP at
> http://www.ntp.org/ntpfaq/NTP-s-trouble.htm arbitrarily rename the files
> to "loops" and "peers", which is what I've been using (and other folks
> too, I'd wager). I'm going to remove those options, but not just yet
> (since I don't want to stitch files together).
>> The primary documentation for NTP is the set of HTML pages, not
>> "manpages".
> Well, you're right.
> http://www.eecis.udel.edu/~mills/ntp/html/confopt.html describes this
> option, as well as the Meinberg docs (which are an earlier version). The
> information seems to be "ungoogleable" in that you must read the whole
> thing top to bottom before you know it exists, but that is of course no
> excuse.
> It is a shame that nothing *outside* the reference documentation (in
> particular quick-start guides) seems to describe the use of this option,
> though. It's also unfortunate that ntpd has been around so long (with
> relatively few changes) that outdated documentation is a dime a dozen.
> I would figure this might fix things, but I'm holding off on that
> because (as you say) this is not friendly on servers and would also not
> fix/identify the root cause -- if my admittedly meager understanding of
> how NTP works is correct, then it shouldn't be necessary to poll the
> servers very frequently unless there's something inherently non-linearly
> wrong with your clock.
> Nothing of the sort. It is a consumer PC used for everything, including
> gaming, and although no gaming has been going on there could in theory
> be some exotic driver or piece of software mucking things up in a
> non-obvious way. If there is, though, I have no idea how to find it
> other than through an extremely tedious bisection that's really not
> worth it. If it turns out that NTP cannot work without stepping my clock
> every so often, I can actually live with that. Not so much if it happens
> on "real" machines, of course. This is strictly a research project.
> It is worth reporting, however, that no stepping has been occurring
> since I first reported the problem. This could be due to a simple
> restart of ntpd and not through any options I've tinkered with. I've
> tinkered with a *lot* of them, and since I'm not a professional
> scientist, I have made no attempt at systematic analysis of all options
> separately and combined, of course, just continued tweaking while I
> wasn't satisfied :-)
> I'm going to leave it alone for a bit to see the results after ntpd gets
> some time to stabilize. For reference, I've done all of the following so
> far:
> - Upgraded to ntpd 4.2.7p310.
> - Replaced individual "server" lines with a single "pool" line.
> - Adjusted power management options within Windows to make processors
> run at 100%.
> - Updated the BIOS. (Also scratched my nose, which I expect has the same
> effect.)
> - Turned off explicit processor frequency stepping options in the BIOS.
> - Used "bcdedit /set useplatformclock on" to force exclusive use of the
> HPET (I'm guessing this does nothing at the moment since interpolation
> isn't used).
> - Last but not least, restarted ntpd.
> Offset are still horrid (>30 ms) but I notice the drift is swinging up
> too, so my guess is that ntpd hasn't fixed on a good value yet after all
> the tinkering (and/or my clock is just bogus for reasons yet unknown).
> If that doesn't work out, I may take apart the network traffic
> (including the DSL router) to see if that has anything to do with
> anything. Delay and jitter on the NTP packets seem fairly high (although
> I don't know if that would explain continuous bad offsets).

NTO restarting - I meant a logical internal restart after a step, not 
the service restarting.

I recall that the NTP Plotter is fairly open to accepting various 
different file names automatically because, as you say, different places 
have different recommendations.  Sigh!  Maybe I'll add a File|Open 
dialog if the program starts with no file specified, but it's not top 
priority at the moment.

Nothing describes "pool"?  Well, my Windows set-up page (also referenced 
by Meinberg) does for a start.

As I mentioned, I haven't tried Internet servers alone recently on 
Windows except for one brief test with Windows-8 (because it has more 
precise time routines):


and I did a test with a Linux server, WAN-only as well:


If precise timekeeping is important, it may be worth upgrading to 
Windows-8 (although I saw an improvement on only one of two PCs tested).

Re IPv6, I turn it off on all of my PCs as I don't use it either.

It may well be that 30 - 40 ms is the best you can expect without some 
local server (e.g. FreeBSD/Linux/Win-8 box on your LAN), but stepping 
every hour should not normally be happening.
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