GDC time sync not working

[James Gardiner]

I have a site asking me about GDC (I am not well inform on GDC) in that the clock is now 3 min slow.
The cinema had a server recently replaced due to a fault.. it had an ntp server on it.. I re-setup the NTP server and tested it was all working fine.
That has not fixed the issue. The SX2100A, when on the interface via VNC, is setup to point at the Linux server running the ntp server.

I was wondering what was the correct way to debug this issue?

Is it possible that the clock has been tweaked so much over the years via ntp that it has reched it limit of variance?
Do I need to contact GDC to get a FIX for it? (A small install that resets the clock variance level?)

Thanks.

[Marcel Birgelen]

There is a 6-time limit of manual clock adjustments for a year, but I'm not entirely sure how that period of a year is determined, as if it follows the calendar and starts on January 1st or if it is triggered by the first "bump". Normal micro-adjustments via NTP should not count towards that limit, but if you're switching NTP servers, you could trigger a "hit" if the delta is too big.

If the machine is still under (extended software) waranty, you can contact GDC and they'll remote into the machine and will fix it for you.

[Dave Macaulay]

For Dolby (Doremi) it is calendar year but I don't know if this is a requirement in DCI spec.
GDC is somewhat opaque on how the system works. Diags pacckages are encrypted, so only GDC can read them. And they won't, if you are out of warranty. Fine, their choice and their right. I prefer Dolby's approach though. Their free and open online analyzer gives a decent overview and a package can be opened and inspected no problem if you want to see the raw logs from some process.

[Steve Guttag]

There are multiple clocks in most servers. If this is still a GDC "Box" server (SX-2100, SX-2001. SX-2000 (with any suffix)...There is the BIOS clock...which is what shows up in the upper-left corner and there is the secure clock, which is best seen from the control panel/System Monitor. At show start, when it checks content and licenses, the Show clock (in the upper-left) should reset to the secure clock. I've noted that GDC's clock is always something like 12-seconds slow.

In any event, by looking at the clock available via the control panel, one can go to the Admin panel to make adjustments (6 minutes/year max). When the clock in the System Monitor agrees with real, then you're good to go. I believe that the NTP clock just affects the Show Clock as the secure clock is not supposed to drift enough to matter (it is supposed to be used for KDM time verification and that's about it).

[Mark Gulbrandsen]

I will add that if a GDC goes beyond the DCI limit, then GDC can remote in to it and run a script to bring it back where it belongs. You WILL need your service agreement up to date with them though.

[John Thomas]

An NTP client typically corrects its clock gradually, by shaving or adding fractions of seconds here and there in order to fall into sync over time. This way there is no major jump in time that would complicate functionality and logging on a running server.

On a Doremi/Dolby, once you set an NTP server, you can reboot and it will jump your RTC to the correct time. Not sure if this is the case on a GDC, but it may be worth checking back in a day or so to see if that 3-minute offset is shrinking. It might just take a few days or a week to see it fully fall back into sync with the NTP server if GDC's don't jump the RTC at boot time.

[James Gardiner]

A GDC tech has suggested, all I need to do is as follows.. there is a section where you can offset the DCI clock..
He suggested I use that. Though not sure exactly how it works. I have this outstanding query with him...

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The DCI adjustable offset defaults to +/- 00:00. meaning MM;SS?? If so I could push the RTC + 03:00 or +3min to get it back in the 1 min range and then the NTP should kick on and bring it into an accurate time?

Note, GDC is 09:04:00 while REAL is 09:07:10 so, +3m10s on GDC clock would bring it roughly into line.

As this is an important change, I just want to make sure I have the right understanding before this is attempted.
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Readers are welcome to comment. Will get back with what happens on here.

[Carsten Kurz]

You can't do anything wrong there. The system will prevent any change larger than +/-6min. And you can change the time back and forth as often as you want within these (absolute) boundaries. Set it to your cell-phone time, then set it to use NTP, and it should lock to NTP in the future.