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I've got a small private network comprised entirely of Macs running Mac OS X 10.6. The computers share files and services. The clocks drift, and this causes problems.

We've tried configuring one of the Macs as an NTP server, but it still drifts and the whole network drifts with it.

Maybe we can connect some kind of hardware clock. Maybe a USB radio clock? I would prefer a Mac-compatible device, but we're prepared to build a whole Linux (or maybe even Windows, if we have to) box to fill this role. I've scoured the Web, and I see things like the WWVB51USB and the USB5131 from Meinberg, but I wanted to see if anybody already had an answer.

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Just a word of warning: If you choose to go down the GPS path for time synchronisation (as many devices do, as it's a cheap, reliable method of getting highly accurate time from the GPS sattelites on-board atomic clock), these can be easilly (and innocently) disrupted by all sorts of behaviour by people in and around the vacinity of your building –  Mark Henderson Apr 15 '11 at 21:14
    
Thanks for the advice! GPS might actually be a very good route for us. Because of the location of the facility, I wouldn't be too worried about jamming or vandalism. –  sidewaysmilk Apr 15 '11 at 21:28
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On the GPS topic, you should ensure the software used to read the time from the receiver has some sanity checks, such as not allowing adjustments over a predefined size. The Mac may even have that built it, as Windows does. –  John Gardeniers Apr 15 '11 at 22:41
    
It looks like Mac's built-in ISC ntpd can speak NMEA to GPS. So we're ordering a $40 Mac-compatible USB GPS off Amazon. I will share my findings when it arrives. Thanks! –  sidewaysmilk Apr 18 '11 at 17:08
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2 Answers

up vote 3 down vote accepted

If you have a convienent window nearby a GPS dongle can provide time information in addition to location.

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We're going with a USB GPS dongle. Snow Leopard's built-in ntpd should work seamlessly with it. –  sidewaysmilk Apr 27 '11 at 19:29
    
Wow! This was a long shot answer. Glad I threw it out there. –  Chris Nava Apr 27 '11 at 19:51
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I definitely can recommend the Meinberg devices. We were using a 19" device which got it's time from DCF77 (Europe) in a large, but closed network (it was a closed production plant network with an Active Directory (don't ask..), so a proper time sync was inevitable for authentication/kerberos etc. The Mainberg device was rock solid, once set up, ran 'forever' - until the plant.. well ;-). Edit: I have no experience with the USB devices.

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Oops, sorry: The device I was talking about ran as a NTP server in the network, so all you would need to do on a Mac is to point it to the IP of the device (System preferences -> Date & Time -> untick "Set date and time automatically" -> enter the IP (or if available the DNS name of the NTP device) in the field besides -> Apply. –  desasteralex Apr 15 '11 at 20:51
    
Still waiting on the quote from Meinberg. An NTP server on DCF77 or similar would be ideal, but probably cost prohibitive. Looks like we're going with a cheap GPS. I'll follow up when it arrives and we hook it up. –  sidewaysmilk Apr 18 '11 at 17:01
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