Film-Tech Forum ARCHIVE: server clocks

This is topic server clocks in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Carsten Kurz (Member # 5396) on 03-05-2011, 01:19 PM:

I understand that DCI servers have two clocks - first a plain-vanilla PC/mainboard/BIOS clock, then a dedicated, secure clock on the IMB. The latter controls KDM validity.

However, the first should be adjustable to allow correct automated show starts (if no external automation/TMS is employed). I read somewhere that DCI allows no more than 6min deviation between the two clocks. However, do the current servers actually comply to this? And in how far is timezone setting affecting this? Most servers seem to disallow PC clock setting, but allow TZ adjustments - I could easily achieve a 24hr shift using the time zone adjustment?

NTP certainly would be an option - but would still not establish a no-drift relationship between server clock and IMB clock. And even NTP could be faked by using your own NTP server.

Any detailed insight?

What happens if you adjust the clock in the BIOS of your server?

- Carsten

Posted by Steve Guttag (Member # 268) on 03-05-2011, 03:09 PM:

Since the clocks and KDMs all reference GMT...changing time zones has zero effect (That is only an offset from GMT).

There are provisions for nudging the clocks but it is limited (something like 20 minutes or less/month and is best done by an NTP server.

While yes it is possible to fake it...the problem is that they limit how much you can drift it per month (and there will be a record of the time change). Both clocks can reference off of the NTP server. That is the best way to keep one's system on time and also provide a uniform reference within the complex.

-Steve

Posted by Carsten Kurz (Member # 5396) on 03-05-2011, 05:30 PM:

You can actually steer both clocks by NTP? It's not so complicate to set up your own NTP server to supply any time you want to the server. Probably NTP will only be configured for servers connected to a NOC under tight control then?

If only the PC clock is synchronized to NTP, it would still drift from the MB clock. But probably so slowly and constantly adjusted that it will not cause any harm?

What happens if you fiddle with the BIOS clock setting too much?

I hear a ot of people have to apply offsets to their show starts because the clocks are running 5-10min off time. Not a real problem, but it seems so stupid. Why can't they just include a NTP server setting in the network setup?

- Carsten

Posted by Joe Redifer (Member # 3) on 03-05-2011, 05:55 PM:

Why aren't the clocks as advanced as my wristwatch which syncs with the atomic clock wirelessly via magic? Seriously, that's just sad.

Posted by Carsten Kurz (Member # 5396) on 03-05-2011, 06:38 PM:

It's too expensive to add motorized legs to the servers so they can walk outside every other day to receive the magic.

- Carsten

P.S. - it seems that more recent Doremi software has a 'Time' tab in system settings. Will this allow ANY time change, or issue a warning if the allowed max shift is exceeded? The Doremi diagnostic system page shows the devication of system and secure clock as xxx/1800s.

Posted by Steve Guttag (Member # 268) on 03-05-2011, 07:31 PM:

While it is true that one can have the NTP time read anything one wants...there is a max/month of shift so even if one wanted to start things an hour early...it would take months of constant resetting to get it to shift that much...and then you would have your clock shutting off legitimate movies an hour early (if you run your features late).

Most servers (if not all) will check their NTP servers at least every restart so cumulative drift would be rendered moot.

-Steve

Posted by Carsten Kurz (Member # 5396) on 03-05-2011, 08:15 PM:

So you mean most servers do have NTP servers configured to sync system time?

- Carsten

Posted by Chris Slycord (Member # 4239) on 03-05-2011, 08:33 PM:

Sounds like he's saying that most servers default checking the time via NTP every time it reboots. And assuming this, if your server is rebooted once per day, it would likely be close enough to the real time at any moment.

Posted by Steve Guttag (Member # 268) on 03-05-2011, 09:01 PM:

Yep, that is what I'm sayin'

Posted by Joe Redifer (Member # 3) on 03-05-2011, 11:25 PM:

quote: Carsten Kurz
It's too expensive to add motorized legs to the servers so they can walk outside every other day to receive the magic.

- Carsten

Hi Cartsen. How are you? Fantastic. If that is the case, I propose the fantastic space-age technology that is employed by the clock hanging on my wall in my basement which sets itself to the atomic clock via radio waves. It is more advanced than any DCI server clock which is, again, just sad that the cinema industry just can't seem to keep up with cheap things sold at Target.

Posted by Mike Blakesley (Member # 26) on 03-06-2011, 12:17 AM:

Joe: the cinema industry shouldn't feel bad though. At my day job I work with a computer system that costs about $25,000 yet it doesn't have the simple feature where you can input dollar amounts without the decimal point and have the computer automatically insert it. The world's cheapest accounting programs can do that. I could go on and on about the frustrations this system causes on a day to day basis but we're stuck with it, because it's companywide.

(The system is called Carquest Exploris and was clearly approved by old men who don't have a clue about computers. It has to be one of the slowest, clunkiest, piece of crap commercial systems out there.)

Posted by Joe Redifer (Member # 3) on 03-06-2011, 01:22 AM:

It seems that the world's best programmers are the ones who aren't being paid to do it.

Posted by Carsten Kurz (Member # 5396) on 03-06-2011, 07:18 AM:

Yes, and the best breed of politicians and economists are driving cabs, cutting hair or shining shoes ;-)

- Carsten

Posted by Carsten Kurz (Member # 5396) on 03-06-2011, 09:25 AM:

Hmm, yep, seems the Dolby DSS200 have an option to set NTP servers by IP-address, either through initial config-script, or later by using the USB Media Block setup application from a connected windows machine.

On the Doremi, you can call cat /doremi/etc/ntpservers to show a list, or initiate a manual sync by executing /doremi/sbin/ntpdate <servername>

For the Dolby, NTP seems to be the only documented way to adjust system time so far.

BTW - a collegue just tried to adjust his Doremi manually, which was running 32min behind. He got a warning: "You have reached the maximum of authorized time range". He was only able to adjust by 30min max. The DCI specs says 'max +/-15min per year', so that seems to be limit. Get rid of the remaining 2min (or whatever it is then) next year ;-)

- Carsten