Timekeeping oddities on MacMini G4s

[Gary E. Miller]

Yo Hal!

On Sat, 04 Feb 2017 17:19:21 -0800
Hal Murray <hmurray at megapathdsl.net> wrote:

> gem at rellim.com said:
> > Then you have to take aging into account.  A 10 year old Mac may
> > have difted a lot.  Or maybe the crystal got bumped.  
> 
> > Also a lot of crystals are now surface mount.  The soldering
> > process may have bend to crystal a lot.   
> 
> Do you have references to any published data?

I have been looking hard for a week.  All I can find is handwaving.

The wikepedia page is typical:

https://en.wikipedia.org/wiki/Crystal_oscillator#Stability_and_aging

Lists of things affecting the crystal, but no real numnbers.

Even the few good data sets I can find are irrelevant unless we
know the specifics of you crystal.  What cut, frequency, model #,
excitation type,  etc.

All I really know is that I have seen motherbaords with frequencies that
are really far off.

Have you chronyd on your Mac yet?  What does it say your frequency is?

> A lot of that depends on what you mean by "a lot".  I haven't seen
> any good rumors that either age or soldering will shift a crystal any
> where near the 500 ppm scale that we are interested in.

This says 'low cost osciallators' are 100 ppm.  So 500 ppm does not seem that
far away to tme.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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