[ntp:questions] Re: ntp client over satellite and no CMOS battery

Martin Burnicki martin.burnicki at meinberg.de
Mon Sep 12 15:12:22 UTC 2005


David,

David J Taylor wrote:
> Martin Burnicki wrote:
> []
>> In fact I've observed that as soon as the first application is
>> started which uses the Windows multimedia timers and sets them to
>> highest resolution of 1 ms (e.g. also Quicktime), the system time
>> reported to normal applications like NTP looses about 15 to 20
>> milliseconds, which looks to NTP as if the system time has been
>> stepped a bit.
> []
>> Martin
> 
> You may want to check if  Windows XP has precisely the same behaviour as
> Windows 2000 and NT4 in this respect.  I mention this because on two PCs
> here, which are used for browsing similar Web sites, Windows XP shows good
> timekeeping:

I've just tried again with Windows XP SP2, and at the first glance it indeed
doesn't seem to happen here anymore. 

However, I'm pretty sure I also observed this under Windows XP when I did my
initial tests a while ago. Maybe this has been fixed in SP1 or SP2.

[...]
> Both systems have QuickTime viewers installed, QuickTime V6.1 on the XP
> system and QuickTime 6.5.2 on the Windows 2000 system.  There's nothing I
> can see in the QuickTime setup about which timers to use, or whether to
> start using multimedia timers immediately on startup.

I think it's not explicitely mentioned in Quicktime, but Quicktime just does
it everytime it starts. The API functions have been added for this purpose
and I don't want to blame the mm applications like Quicktime on this. What
was really poor was the side-effect on the normal Windows system time,
which is a problem of the Windows design or implementation.


Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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