[ntp:questions] Re: ntp client over satellite and no CMOS battery
David J Taylor
david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Sun Sep 11 06:58:36 UTC 2005
Brad Knowles wrote:
> At 5:45 PM -0400 2005-09-10, Richard B. Gilbert wrote:
>
>>
>> Some hardware and software can do this very well indeed. Others;
>> e.g. Windows and Linux do not do nearly so well.
>
> Linux can do fine, assuming the hardware is good, and the
> OS/software configuration is good. More recent versions of Linux
> have tended to have some kernel issues that require rebuilding with
> different options, if you want to be able to keep good time. But
> once that is done, you should be okay.
>
> Unfortunately, Windows does not give you such an option, and
> unless the server is pretty much totally unloaded and dedicated to
> running nothing but NTP, you are likely to suffer some accuracy
> problems.
Here is what my Windows systems synced off the Internet achieve:
http://www.david-taylor.myby.co.uk/mrtg/daily_ntp.html
For some reason (which I would love to sort out!), this Windows 2000
system has problems when certain Internet sites are accesses, possibly
those using Flash:
http://www.david-taylor.myby.co.uk/mrtg/stamsund_ntp.html
This system runs a real-time data capture system with Windows NT 4.
http://www.david-taylor.myby.co.uk/mrtg/bacchus_ntp.html
This system is used for compiling and CPU-intensive tasks:
http://www.david-taylor.myby.co.uk/mrtg/odin_ntp.html
and this system runs a satellite data terminal at about 2Mb/s continuous
and shares the resulting files to the network:
http://www.david-taylor.myby.co.uk/mrtg/hermes_ntp.html
In general, all these last three systems keep within 10-20ms of correct
time, and have only been worse than that across a power glitch or across a
restart of NTP.
The Windows NT 4 system was restarted recently following a power glitch
after being up for about a year continuous, and the CMOS had drifted quite
a bit. Normally, stopping NTP would update the CMOS time, but if the
power stops (and no UPS here) the CMOS will have been running at its own
rate since system startup.
David
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