How to synchronize clocks on two PCs?

[blawson]

Been tangling with this problem: I have two PC-based data sources whose clocks I'd like to keep synchronized within ~25ms.  They share an ethernet x-over connection on static IPs.  Machine A is my deployment target, Machine B is a device controller that I have essentially user access to.  Both are Windows XP PCs.  No net connection exists. The two machines are only connected when my software is in use.  Tests run ~1hr max.

I tried using the Windows Time Service ( w32tm and W32Time ) to synchronize two XP machines.  I followed this MS article on how to configure xp as an NTP time server, and set the client up to sync from it. http://support.microsoft.com/kb/314054/.  I  got it working and got it to correct a 16second difference between the machines, but it doesn't seem to do anything if there's an offset under 1sec.  in http://support.microsoft.com/kb/939322best , MS claims that 1-2sec is the limit of the software.

Has anyone used a different NTP setup?  I see a few posts involving NTP and cRIO, is there any application of that here?

[Ben]

Do you need to sync them WITHOUT a network connection?

If you have a network, you could use UDP to transmit sync packets after you benchmark the transport time.

Otherwsie IRIG-B interfaces (don't remeber the NI borad that supports it) will let you sync to the GPS clocks.

Ben

[Rod42]

Hi blawson,

Have a look at www.arachnoid.com/abouttime/

It has a program that can be a network time server or client. That may do what you need

Rod.

[blawson]

-sorry if it wasn't clear enough: computers are networked peer-to-peer with no internet connection.

though W32Time is trying to *keep* computers synchronized, all I want to do is force one computer to sync off another on command.

I've discovered that with the proper network sharing setup, "net time \\computername /set /yes" on a command line will do what I want.