[ntp:questions] ntpd wedged again

David Lord snews at lordynet.org
Wed Feb 15 12:07:14 UTC 2012


A C wrote:
> On 2/14/2012 01:49, David Lord wrote:
>> 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
>> ....
> 
> I have timecounter in my dmesg also but it doesn't show up anywhere in 
> the kernel configuration for compiling:
> 
> # dmesg | grep time
> timecounter: Timecounters tick every 10.000 msec
> timer0 at mainbus0 ioaddr 0xf3000000 ipl 10: delay constant 18, 
> frequency = 1000000 Hz
> timecounter: Timecounter "timer-counter" frequency 1000000 Hz quality 100
> timecounter: Timecounter "clockinterrupt" frequency 100 Hz quality 0
> 
> I'll have to ask the NetBSD people where the value is hiding.

Most likely my config is i386 specific but it's possible
there are other methods to adjust the frequency.  From your
dmesg it looks to be your clock is at 1 MHz.

I searched through my NetBSD-5 docs and can't find mention
of TIMER_FREQ. The means of adjustment by that options line
does still work on i386 though. I've grepped /usr/src/sys/arch
for that text and it does appear in other arch besides i386
but not sparc or sparc64.


David



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