[ntp:questions] ntpd wedged again

David Lord snews at lordynet.org
Tue Feb 14 09:49:55 UTC 2012


A C wrote:
> On 2/13/2012 15:44, David Lord wrote:
> 
>> Recent ntpd is supposed to handle that level of frequency
>> offset but most of my pcs have had the frequency offset
>> adjusted to be < 10 ppm which is done when I build a kernel
>> with "options PPS_SYNC" and "options TIMER_FREQ=119????".
> 
> This kernel does have PPS_SYNC enabled but I'm not using it right now 
> since I'm still debugging ntpd/libc.  I'll start using it next week 
> after I know ntpd will survive a week straight.
> 
> How do you determine the timer frequency number?  Trial and error?

At one time I could find it in the documentation but
not when I last did a search.

AFAIK it was supposed to be self calibrating so the
ability for adjustment might be dropped. Unfortunately
the self calibration can be > 50ppm out.


PC me6000 is using kernel compiled for a different pc:
me6000 $ dmesg | grep timecounter
....
timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
....
me6000 $ cat /var/db/ntp/ntpd.drift
-35.834
me6000 $ ntpq -p
remote         refid  st  poll reach  delay   offset  jitter
*GPS_NMEA(2)  .GPSb.   0    16   377  0.000  -34.509  18.290
oPPS(2)       .PPSb.   0    16   377  0.000   -0.001   0.004
....

p4x2400b $ dmesg | grep timecounter
....
timecounter: Timecounter "i8254" frequency 1193110 Hz quality 100
....
p4x2400b $ cat /var/db/ntp/ntpd.drift
-9.358
p4x2400b $ ntpq -p
remote         refid  st  poll reach  delay   offset  jitter
*me6000       .PPSb.   1    64   376  1.573    0.559   0.517
....
+ntp0         .MSFa.   1  1024   375  1.811    1.905   2.614


David



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