[ntp:questions] 500ppm - is it too small?

Unruh unruh-spam at physics.ubc.ca
Fri Nov 13 16:58:49 UTC 2009


David Woolley <david at ex.djwhome.demon.invalid> writes:

>Unruh wrote:
>> David Woolley <david at ex.djwhome.demon.invalid> writes:
>> 
>>> Unruh wrote:
>> 
>>>> The problem is that Mills hardcoded this into the kernel routines for
>> 
>>> It, and lower values, e.g. 100ppm where hardcoded into kernels before 
>>> nptd was a factor.  The interface that ntpd uses in user space mode 
>>> typically had this sort of limit.
>> 
>> I believe Mills was largely responsible for the kernel time routine
>> (like adjtimex) 
>> ntp has been around for about 20 years now, longer than Linux has. 

>I'm talking about adjtime.  adjtimex was clearly intended for ntpd.

adjtime does not change the rate at all except to eliminate the input offset. Ie,
you cannot use it to slow down or speed up the clock in a predictable manner. You
give it an offset and it slows down or speeds up the clock to eliminate that
offset ( something like the adjtimex -s option. And that does not limit itself to
500ppm.AFAIK)


>> 




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