[time-nuts] 10MHz standard for comms receivers

Hal Murray hmurray at megapathdsl.net
Tue Oct 2 19:35:24 EDT 2018


> My macbook air shows 56.652 in ntp.drift

That can be software (kernel) error as well as crystal tolerance.

There are 2 ways of calibrating the CPU clock.  One is to wire in a magic 
number in the kernel timekeeping.  The other is to measure it against some 
clock of known frequency.

Several years ago, the Linux kernel would get different answers each time you 
booted it.  Close enough so that an individual answer looked reasonable, but 
not good enough if you expected ntp.drift to be close when you rebooted.



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