[time-nuts] Syncing Computer to Datum 9700 Programmable Time System

Fri Jan 4 19:14:30 UTC 2008

Howdy, all!

Since I retired from the Air Force a year ago, I've been intrigued with how
well my Datum 9700AT (going away present from my crew) keeps time compared
to all the computers and clocks in the house.  While it's not a cesium-based
standard, or even GPS-updated, it does pretty darned well over the course of
a year.  

I noticed all the wonderful outputs on the back, and I'd like to take the
1PPS signal and use it as a timing standard for my IBM workstation running
XP Pro SP2, thereby making it the home time server for the rest of our
computer network.  I'm assuming that it would have to go into one of the
available serial ports, but is there an off-the-shelf cable w/software to
enable this, or am I heading into uncharted territory?

Thanks for letting me pick the group's collective brains!

Darin R. Pfaff
Sun Prairie, WI

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of time-nuts-request at febo.com
Sent: Friday, January 04, 2008 12:49 PM
To: time-nuts at febo.com
Subject: time-nuts Digest, Vol 42, Issue 9

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Today's Topics:

   1. Re: sync computer clock ticks (Keith Payea)
   2. Re: sync computer clock ticks (M. Warner Losh)
   3. FW:  sync computer clock ticks (David Moisan)
   4. Re: sync computer clock ticks (michael taylor)
   5. Re: sync computer clock ticks (M. Warner Losh)
   6. Re: FW:  sync computer clock ticks (Keith Payea)
   7. Re: FW:  sync computer clock ticks (Jack Hudler)
   8. Re: CPU frequency and NTP crazyness. (Christian Vogel)
   9. Re: sync computer clock ticks (Christian Vogel)

----------------------------------------------------------------------

Message: 1
Date: Fri, 4 Jan 2008 09:01:14 -0800
From: "Keith Payea" <kpayea at bryantlabs.net>
Subject: Re: [time-nuts] sync computer clock ticks
To: "'Discussion of precise time and frequency measurement'"
	<time-nuts at febo.com>
Message-ID: <012e01c84ef3$6ab81ed0$0a01a8c0 at bryant1>
Content-Type: text/plain;	charset="us-ascii"

Michael:

What NTP software are you using? Many are intended just to keep the clock
within a second, and don't work very hard at it.

The best is to get a port of the "real" NTP from the source at
http://www.ntp.org/  They have ports for most major OS's.  You should be
able to maintain better than 10 milliseconds to UTC once it has settled for
a while.

Also be sure to check out the NTP server pool project at
http://www.pool.ntp.org/.  It's an effort to spread out the load on major
NTP servers.

    Keith

Keith Payea
Bryant Labs
kpayea at bryantlabs.net
www.bryantlabs.net
(707) 566-8935

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Michael Di Domenico
Sent: Friday, January 04, 2008 6:00 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] sync computer clock ticks

I've used NTP for years, but i was under the impression that it is not
able to synchonize the clocks below 1 or 2 seconds.   Can you point me
towards a specific article that speaks about the configuration
parameters to get ntp sync'd that low?

On Jan 3, 2008 10:25 PM, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
>
> Michael Di Domenico wrote:
> > This has probably been asked many times before, but i am unable to
> > find any documentation to point me in the right direction.  And yes i
> > am a newbie with clocks...
> >
> > I'd like to synchronize the clock ticks on 16 different computers
> > running linux, down to the 1usec area.  Is this even possible from a
> > computer hardware standpoint?
> >
> > If so, can someone point me towards some documentation that explains
> > how to wire up 16 computers to a reference clock source and override
> > the computer internal clocks?
> >
> > I found the Symetricom website, but it seems light on details on
> > exactly how a solution like this all connects together and they're
> > products are likely outside my budget.
> >
> > Ideally, I'd like to use the serial port on each of these 16 servers
> > to connect to some device to get the synchronization signal from a
> > reference.  Even if this was possible, i don't think it would get me
> > to 1usec though.
> >
> > Thanks
> > - Michael
> >
> >
> Michael
>
> Google ntp.
>
> It is unlikely that you will synchronise the computer clocks to within
> 1us with ntp unless the computer hardware and operating system is
> suitably modified.
> This can be done cheaply (one machine needs to be setup as a dedicated
> stratum 1 ntp server synchronised to a good time source like a M12M gps
> timing receiver or equivalent device).
> NTP broadcasts the required info as LAN packets.
>
> If you really need that precisionyou may need to use ptp with suitable
> hardware (National Instruments and others have suitable boards)
> NIST has a webpage on PTP.
>
>
> Bruce
>
>
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>

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------------------------------

Message: 2
Date: Fri, 04 Jan 2008 10:03:41 -0700 (MST)
From: "M. Warner Losh" <imp at bsdimp.com>
Subject: Re: [time-nuts] sync computer clock ticks
To: time-nuts at febo.com, mdidomenico at gmail.com
Message-ID: <20080104.100341.-1350533844.imp at bsdimp.com>
Content-Type: Text/Plain; charset=us-ascii

In message: <97a7c7ed0801040600x5d2781cfl40e31dd70731492c at mail.gmail.com>
            "Michael Di Domenico" <mdidomenico at gmail.com> writes:
: I've used NTP for years, but i was under the impression that it is not
: able to synchonize the clocks below 1 or 2 seconds.   Can you point me
: towards a specific article that speaks about the configuration
: parameters to get ntp sync'd that low?

I don't know about other people, but out of the box I get sub 20ms
synchronization.  Right now, it is sitting at about 12.5ms:

     remote           refid      st t when poll reach   delay   offset
jitter
============================================================================
==
*xxxxx.yyyyyy.co 10.7.1.1         2 u  965 1024  377   64.176  -12.570
0.508

My config file is just a simple:

server 1.2.3.4   # xxxxx.yyyyyyy.com

driftfile /mod/etc/ntp.drift

restrict default notrust nomodify

restrict 127.0.0.1
restrict 1.2.3.4
restrict 10.0.0.6
restrict 10.0.0.0 mask 255.255.0.0 notrust

------------------------------

Message: 3
Date: Fri, 4 Jan 2008 12:13:23 -0500
From: David Moisan <dmoisan at davidmoisan.org>
Subject: [time-nuts] FW:  sync computer clock ticks
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID:

<A4BE6F17905C1D45BB06807F0D80D3A92CE24A8E at SKIPPY.DMPRODUCTIONS.local>
Content-Type: text/plain; charset="us-ascii"

-----Original Message-----
From: David Moisan
Sent: Friday, January 04, 2008 11:43 AM
To: Discussion of precise time and frequency measurement
Subject: RE: [time-nuts] sync computer clock ticks

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: Friday, January 04, 2008 9:17 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] sync computer clock ticks

>Challenges may be (a) in the Windows world, earlier versions (prior to
>some SP level of XP) have inherent limitations on timekeeping accuracy,

I have considerable experience with Windows networks.  Windows 2000 time
clients are the worst, XP is better and Server 2003 best of all.  Vista and
Windows 2008 are based on the 2003 code.  My workplace is a public access TV
station and our biggest challenge is getting consistent time without being
able to pay for nice things like IRIG displays or GPS clocks.  It doesn't
help that our master controller is Windows 2000 based with a flaky CMOS
clock that was caused by renovations in the room it was installed in.

Symmetricom has a app for Windows networks, LMCheck, that can check for
variance.
http://dtdocs.ntp-systems.com/software/domaintime/instructions/tools/lmcheck
.asp

------------------------------

Message: 4
Date: Fri, 4 Jan 2008 12:18:53 -0500
From: "michael taylor" <mctylr at gmail.com>
Subject: Re: [time-nuts] sync computer clock ticks
To: "Discussion of precise time and frequency measurement"
	<time-nuts at febo.com>
Message-ID:
	<25630a120801040918x2203daebs7eb0de5f00ffc56c at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

On Jan 4, 2008 12:03 PM, M. Warner Losh <imp at bsdimp.com> wrote:
>
> I don't know about other people, but out of the box I get sub 20ms
> synchronization.  Right now, it is sitting at about 12.5ms:
>
>      remote           refid      st t when poll reach   delay   offset
jitter
>
============================================================================
==
> *xxxxx.yyyyyy.co 10.7.1.1         2 u  965 1024  377   64.176  -12.570
0.508
>

That's a 12 ms offset from UTC, as far as I understand the original
poster only needs  <= 1 microsecond synchronization on his local
network.

-Michael

------------------------------

Message: 5
Date: Fri, 04 Jan 2008 10:28:33 -0700 (MST)
From: "M. Warner Losh" <imp at BSDIMP.COM>
Subject: Re: [time-nuts] sync computer clock ticks
To: time-nuts at febo.com, mctylr at gmail.com
Message-ID: <20080104.102833.1021541154.imp at bsdimp.com>
Content-Type: Text/Plain; charset=us-ascii

In message: <25630a120801040918x2203daebs7eb0de5f00ffc56c at mail.gmail.com>
            "michael taylor" <mctylr at gmail.com> writes:
: On Jan 4, 2008 12:03 PM, M. Warner Losh <imp at bsdimp.com> wrote:
: >
: > I don't know about other people, but out of the box I get sub 20ms
: > synchronization.  Right now, it is sitting at about 12.5ms:
: >
: >      remote           refid      st t when poll reach   delay   offset
jitter
: >
============================================================================
==
: > *xxxxx.yyyyyy.co 10.7.1.1         2 u  965 1024  377   64.176  -12.570
0.508
: >
: 
: That's a 12 ms offset from UTC, as far as I understand the original
: poster only needs  <= 1 microsecond synchronization on his local
: network.

I have no experience with gige networks, but the best I've been able
to do on 100baseT networks is 50us.  I'm unsure what <1us
synchronization really means, since that's starting to get below the
level of system calls on fast machines.

Warner

------------------------------

Message: 6
Date: Fri, 4 Jan 2008 09:33:52 -0800
From: "Keith Payea" <kpayea at bryantlabs.net>
Subject: Re: [time-nuts] FW:  sync computer clock ticks
To: "'Discussion of precise time and frequency measurement'"
	<time-nuts at febo.com>
Message-ID: <013501c84ef7$f99a5970$0a01a8c0 at bryant1>
Content-Type: text/plain;	charset="us-ascii"

The NTP built into Windows is very poor.  A couple of the versions are not
even compliant with the standard, and some servers will reject their
requests.  You have to use better client software, at least for your master
controller.

The CMOS clock only matters when you lose power.  NTP should only use it
once at start-up as a sanity check.

	Keith

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David Moisan
Sent: Friday, January 04, 2008 9:13 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] FW: sync computer clock ticks

-----Original Message-----
From: David Moisan
Sent: Friday, January 04, 2008 11:43 AM
To: Discussion of precise time and frequency measurement
Subject: RE: [time-nuts] sync computer clock ticks

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: Friday, January 04, 2008 9:17 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] sync computer clock ticks

>Challenges may be (a) in the Windows world, earlier versions (prior to
>some SP level of XP) have inherent limitations on timekeeping accuracy,

I have considerable experience with Windows networks.  Windows 2000 time
clients are the worst, XP is better and Server 2003 best of all.  Vista and
Windows 2008 are based on the 2003 code.  My workplace is a public access TV
station and our biggest challenge is getting consistent time without being
able to pay for nice things like IRIG displays or GPS clocks.  It doesn't
help that our master controller is Windows 2000 based with a flaky CMOS
clock that was caused by renovations in the room it was installed in.

Symmetricom has a app for Windows networks, LMCheck, that can check for
variance.
http://dtdocs.ntp-systems.com/software/domaintime/instructions/tools/lmcheck
.asp

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To unsubscribe, go to
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------------------------------

Message: 7
Date: Fri, 4 Jan 2008 12:14:46 -0600
From: "Jack Hudler" <jack at hudler.org>
Subject: Re: [time-nuts] FW:  sync computer clock ticks
To: "'Discussion of precise time and frequency measurement'"
	<time-nuts at febo.com>
Message-ID: <000901c84efd$b10a3df0$131eb9d0$@org>
Content-Type: text/plain;	charset="US-ASCII"

I use a Truetime NTS-100 for my NTP server.
Just scanned my network of Windows machines at home, all using MS NTP
Client. 3-Vista, 2-2003 Server, 1-XPSP2.
Worst 11 ms, average variance is 2ms.

Jack

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Keith Payea
Sent: Friday, January 04, 2008 11:34 AM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] FW: sync computer clock ticks

The NTP built into Windows is very poor.  A couple of the versions are not
even compliant with the standard, and some servers will reject their
requests.  You have to use better client software, at least for your master
controller.

The CMOS clock only matters when you lose power.  NTP should only use it
once at start-up as a sanity check.

	Keith

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David Moisan
Sent: Friday, January 04, 2008 9:13 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] FW: sync computer clock ticks

-----Original Message-----
From: David Moisan
Sent: Friday, January 04, 2008 11:43 AM
To: Discussion of precise time and frequency measurement
Subject: RE: [time-nuts] sync computer clock ticks

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of John Ackermann N8UR
Sent: Friday, January 04, 2008 9:17 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] sync computer clock ticks

>Challenges may be (a) in the Windows world, earlier versions (prior to
>some SP level of XP) have inherent limitations on timekeeping accuracy,

I have considerable experience with Windows networks.  Windows 2000 time
clients are the worst, XP is better and Server 2003 best of all.  Vista and
Windows 2008 are based on the 2003 code.  My workplace is a public access TV
station and our biggest challenge is getting consistent time without being
able to pay for nice things like IRIG displays or GPS clocks.  It doesn't
help that our master controller is Windows 2000 based with a flaky CMOS
clock that was caused by renovations in the room it was installed in.

Symmetricom has a app for Windows networks, LMCheck, that can check for
variance.
http://dtdocs.ntp-systems.com/software/domaintime/instructions/tools/lmcheck
.asp

_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
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and follow the instructions there.

------------------------------

Message: 8
Date: Fri, 04 Jan 2008 19:39:18 +0100
From: Christian Vogel <vogelchr at vogel.cx>
Subject: Re: [time-nuts] CPU frequency and NTP crazyness.
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <477E7D56.4060103 at vogel.cx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Ryan,

> maximum speed and everything has been just peachy with NTP. My
> question is this, does anyone have a way to switch off the power save
> feature the CPU is using so I don't have to run my machine full tilt?

you can do it by changing different power-schemes in Windows' 
Control-Panel Power Properties.

Download RMclock to watch your CPUs clocks and voltage/frequency 
settings while playing with the power-schemes.

If you select "Always On", your computer will not do any power-saving.

	Chris

------------------------------

Message: 9
Date: Fri, 04 Jan 2008 19:48:49 +0100
From: Christian Vogel <vogelchr at vogel.cx>
Subject: Re: [time-nuts] sync computer clock ticks
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <477E7F91.60601 at vogel.cx>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Michael,

> I've used NTP for years, but i was under the impression that it is not
> able to synchonize the clocks below 1 or 2 seconds.   Can you point me
> towards a specific article that speaks about the configuration
> parameters to get ntp sync'd that low?

at work, I use it to sync all servers and workstations to 4 stratum 1 
NTP-servers. I get ~100us offset usually. Without special hardware I'd 
say that 1usec is not possible.

Server, Gig-Ethernet, 4 hops (>=Gigabit) to ntp:
*ntp2-rz.rrze.un .GPS. 1 u  758 1024 377 1.225 **-0.179** 0.068
(HP DL380-G3, Dual 3.2 GHz P4, no powersaving)
-> Temperature fluctuates +/- 3 Deg-Celsius every 20sec due to HVAC

Client, 100Mbit, 5 hops (last 4 are better than Gigabit):
*ntp2-rz.rrze.un .GPS. 1 u  987 1024 377 1.577 **-0.111** 0.091
(P4-Celeron, 2.4 GHz, currently throttled to 300 MHz)
-> Temperature currently stable and possibly very cool, have not
  been in my office for a week :-)

My main problem is probably that ntp switches between three equally good 
servers quite frequently (it just did).

      Chris

------------------------------

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