> I think that that's Dan's point -- /var/db/ntp.drift is for state
> between boots.  It's supposed to measure the difference over time
> between your machine's clock and reality, and you rarely switch
> clocks.  It isn't supposed to compensate for the errors in your ntp
> peers; ntp assumes that there's One True Time, and doesn't use
> averaging, for example.
> 
> 
> 		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb

right. so if you switch internal clock models, the ntp.drift is
inherently invalid, and the right thing (tm) is to junk it.

-George