Re: how to analyze clock drift

[brbarkstrom@gmail.com]

On Monday, November 24, 2014 1:28:59 PM UTC-5, Dmitry A. Kazakov wrote:
> On Mon, 24 Nov 2014 12:24:15 -0500, Dennis Lee Bieber wrote:
> 
> > On Mon, 24 Nov 2014 09:44:39 +0100, "Dmitry A. Kazakov"
> > declaimed the following:
> > 
> >>Setting THREAD_PRIORITY_TIME_CRITICAL blocks practically everything (except
> >>for drivers).
> >>
> >>However I doubt that background processes or services are the problem when
> >>waiting for 10 or 5ms
> >>
> > 	Many moons ago I had a task using a GFE W98 (!) laptop [needed to be
> > W9x to allow direct access to the parallel port].
> 
> Windows 98 cannot be compared with NT.
> 
> > Wasn't a timer situation
> > -- it was more a busy wait since the main timing control was obtained from
> > an external (1KHz as I recall) clock to a signal pin on the parallel port.
> > The task required writing 6-bits on each clock transition (I forget if
> > L->H, or H->L) -- the 6-bits representing three RS-422-style balanced data
> > lines... 
> 
> You should have written a proper driver for this with interrupts and
> deferred I/O.
> 
> BTW, TIME_CRITICAL blocks even deferred I/O processing, if I correctly
> remember. Windows internals are not that bad as painted.
> 
> -- 
> Regards,
> Dmitry A. Kazakov


If you want to get time standard information, you can start with the
very short background piece from Wikipedia:

http://en.wikipedia.org/wiki/Standard_time_and_frequency_signal_service

The US Government Agency that maintains time standards is a division within
the National Institute of Standards and Technology (NIST).  They broadcast
time signals from WWV.  The Web page that provides the entry to this
information is

http://www.nist.gov/pml/div688/grp40/wwv.cfm

The following page gives suggestions on how to access time signals from
a computer connected to the Internet:

http://www.nist.gov/pml/div688/grp40/its.cfm

The following pdf has information on computer time-keeping, although I'm
not sure what its date is.  Even so, this may be useful reading.

http://tf.nist.gov/service/pdf/computertime.pdf

A standard reference on time and related astronomical matters is

Seidelmann, P. K., 2006: Explanatory Supplement to the Astronomical
Almanac: Completely Revised and Rewritten, University Science Books,
Sausalito, CA.

If you want to look into algorithms with a modern (Bayesian) flavor,
you might look at

Pole, A., West, M., and Harriaon, J., 1994: Applied Bayesian Forecasting
and Time Series Analysis, Chapman & Hall/CRC, Boca Raton, FL

This is pretty readable, even though it may seem a bit old.  There's
an interesting (and probably useful) piece of DOS software that might
be fun to update if you can get copyright permission and have some
spare time.  If your taste runs to much fancier math, there's a whole
special interest group of the Society of Industrial and Applied Mathematics
(SIAM) that's devoted to Uncertainty Quantification.

Sorry to be a bit late in responding.

Bruce B.