[ntp:questions] Come back PPS I miss you!

David J Taylor david-taylor at blueyonder.co.uk.invalid
Sat Feb 11 15:28:34 UTC 2012

>>  http://www.satsignal.eu/mrtg/daily_ntp.html
> Alta's graph on that page is scaled inappropriately for its current
> performance level.  Follow the link at the top of the page to the
> Alternative Presentation and you'll find a graph of alta with a more
> useful scale (albeit also a different style with the absolute value of
> the offset as the Y scale and a different color to indicate
> negatives).
> Cheers,
> Dave Hart

Correct.  Like most of my PCs, PC Alta was never designed as a stratum-1 
server, but as I happened to have a second Sure Electronics GPS board 
which needed testing, and as using an unsigned driver on 64-bit Windows 
was one of those "You can't do that" challenges, it just happened!  I have 
now added an additional graph scaled +/- 500 microseconds to compare with 
the other starum-1 Windows servers. (The FreeBSD graph is scaled +/- 20 
microseconds, by the way).  It will take the data some time to populate 
the new graphs, of course.  PC Alta also functions as a virtual radar 
using the Plane Plotter software and ADS-B receiver, receives about 40 GB 
of data per day over a digital satellite feed, and process that data into 
weather images, so I am not expecting it to be the most stable of Windows 
stratum-1 servers.

I have also added more appropriate graphs for the Windows 2000 server, PC 
Bacchus, which is also an accidental stratum-1 server, working from a 
paralleled serial feed from a GPS 18 LVC.  It also receives weather 
satellite data, but this time from a 137 MHz audio feed (APT) which it 
demodulates into image data, and serves over the network.  It's quite 
old - a 550 MHz Pentium III (if anyone remembers those!).  When the disk 
drefrag runs on Wednesday it hammers the timekeeping, even on the old 
graph scale.

I have some loopstats files if anyone is /that/ interested.

Thanks for the prompt to enhance this.


More information about the questions mailing list