Re: Dual-core system will not create NTP peers

[Moshe Yudkowsky <moshe@pobox.com>]

I have discovered the source of the problem: the file 
/etc/default/adjtimex had a TICK value of 9750. That's 2.5% less than 
the standard value of 10000 and accounts exactly for the clock skew I 
observed.

I adjusted the tick back to a reasonable value (see below) and my clock 
problems appear to be solved.

I have no idea how the file obtained this value. I suspect that when 
adjtimex was installed, the package used /usr/sbin/adjtimexconfig and 
that it somehow obtained completely incorrect values.

To adjust tick and frequency for maximum accuracy, I highly recommend 
Larry Dolittle's ntpclient package at 
<http://doolittle.icarus.com/ntpclient/>. In particular, the HOWTO file 
not only explains the debug output of his tools but also gave me 
invaluable information that I could use to resolve my own problem.

Math notes to future readers, since "tick" can be confusing: the tick is 
"how many microseconds to add to the current clock reading." Ticks occur 
100 times per what the system thinks is a second, and if the value of a 
tick is set to 10000, then it will add 100 * 10,000 = 1,000,000 
microseconds to the system clock each second. Because the value of the 
tick in my system was set to 9750, each second I added only 975,000 
microseconds to the system clock, for a deficit of 2.5%. See the 
adjustimex man page as well as Larry's HOWTO page.
--
Moshe Yudkowsky * moshe@pobox.com * www.pobox.com/~moshe
 "Only a fool fights in a burning house."
                                           -- Ancient Klingon Proverb