[LinuxPPS] Why is my ATOM clock a falseticker?

[Paul Simons]

Surprizingly, it is CONFIG_HZ=250.  Is that the default?  Should I change it to 100?

On 01/31/2009, "Cirilo Bernardo" stated:

> On Sat, Jan 31, 2009 at 9:46 AM, Paul Simons <paul at thesimonet.org> wrote:
>> Oops, here is the relevant section:
>>
>> server 127.127.22.1 minpoll 4 maxpoll 4 # ATOM (PPS)
>> fudge 127.127.22.1 flag2 1              # Use the "clear" edge of the signal
>>
>> # "PPS pulses are usually short, and the leading edge is the on-time mark,
>> # so by looking at the time of two adjacent edges with cat
>> /sys/class/pps/pps1/{assert,clear},
>> # you can see which one leads the other."
>>
>> server 127.127.5.0 prefer               # TrueTime clock
>> #No fudge
>>
>
> I suspect the problem is with putting 'prefer' into the 127.127.5.0
> source.  If that is an ASCII string then there will be a lot of jitter
> in it and may have an unwanted effect on NTP.  If that is a problem
> then ntp or Linux has a bug because the interval between PPS pulses
> should be much more stable than the ascii string put out by a clock.
>
> What is your setting for CONFIG_HZ in the kernel options?
>
> - Cirilo
>


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