David Lord wrote:
> I use ntpd to sync to internet time. A few of my pcs have clocks too 
> far out for ntpd to work effectively as the natural clock drift is at 
> a greater rate than ntpd can lock to. The fix is to adjust the value 
> of TIMER_FREQ in kernel configuration to offset the system clock 
> drift. I aim for within -10 ppm to 0 ppm. Of course temperature and 
> power supply voltage can cause fairly wide variation so near is good 
> enough vs >>500 ppm drifts of some pcs. Other pcs are within 30 ppm 
> without any tweaking. 
> 
> eg. from K6X400_0.32
> ! # K6X400 is approx -60 ppm so aim for > +50ppm change
> ! # default 1193182
> ! # for +68
> ! options  TIMER_FREQ=1193250

Thank you, David.  This is very helpful, if still a bit mysterious. 
Here's what I'm seeing:

cherry$ grep ntpd /var/log/messages |head 
Nov 15 11:09:29 cherry ntpd[29870]: time reset -2.326574 s
Nov 15 11:09:29 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 11:14:53 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 11:34:10 cherry ntpd[29870]: time reset -3.754409 s
Nov 15 11:34:10 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 11:39:33 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 11:54:35 cherry ntpd[29870]: time reset -2.699728 s
Nov 15 11:54:35 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 11:59:57 cherry ntpd[29870]: frequency error -512 PPM exceeds
tolerance 500 PPM
Nov 15 12:16:59 cherry ntpd[29870]: time reset -3.915989 s

cherry$ config -x /netbsd | grep TIMER  
options         TIMER_FREQ=1189200

I don't know what units TIMER_FREQ is in.  Taking a naive guess, I add 512
to it, giving me 1189712.  Since you suggest overcompensating, perhaps
1189800?  

Is that the idea?  

--jkl