William R. Walsh wrote:
It's an RC oscillator circuit. The schematic shows an adjustable resistor.
None of my units have that--there is a fixed resistor. I cannot tell what
the value of the capacitor should be...guessing 60pF?

I forgot to mention--in my working toys, the clock still appears to wander,
but much less severely. It seems to fluctuate based on whatever the
microcontroller is doing.

Lacking in-depth experience with these circuits, I also want to be sure
whether I'm on the right track or not.

That dithered clock is a technique we use to make it
appear that our designs are 'quieter' than they really
are, RF noise - wise.

http://www.maxim-ic.com/app-notes/index.mvp/id/1995

Since all parts of the circuit see the same clock, everything
remains synchronized.

Relativity in action!

--Winston