Chris, I have one NTP GPS based server running locally but I wanted to also setup the Mac with the Thunderbolt as a second NTP server. This way instead of using an external NTP server as a backup I would have a second local server. The Mac is Unix based and has a built in NTP server but it is normally disabled. If I enable the server isn’t it going to pull its time from the system clock ? This is the only reason I care about the system clock. Maybe I am approaching this incorrectly. Maybe the question should be how to get a local NTP server to use LH/Thunderbolt ? > > From: Chris Albertson <albertson.chris@gmail.com> > Subject: Re: [time-nuts] Local System Time Sync > Date: July 26, 2017 at 0:23:15 EDT > To: Lee - N2LEE <lee@n2lee.com>, Discussion of precise time and frequency measurement <time-nuts@febo.com> > > > You should be using NTP for that. > > Simply "syncing" the local clock to GPS is never the best thing to do. If > you think about it 50% of the time the local clock would have to go > backwards and 50% forwards. This means you could have the system time be > at the same time twice or you have missing time intervals. > > The correct way is to adjust the RATE of the local clock so you never have > missing or double time. This is exactly the same as building a GPSDO. > Every adjustment period you compare there PHASE of the local clock to GPS > then adjust the RATE if required. NTP does this. > > On Tue, Jul 25, 2017 at 7:45 PM, Lee - N2LEE via time-nuts < > time-nuts@febo.com> wrote: >