What about SNTP (e.g., Windows)

Previously:

Leap Seconds
State of the Standards
What Matters When measuring
The UNIX-NTP real world compromise

Windows and many others normally use SNTP for time synchronization. What about all those machines?

For all the administrative scopes this is no problem.  SNTP lacks the frequency controls provided by NTP, so these systems will suffer from the occasional severe frequency glitch.  SNTP as typically configured for Windows can also cause phase errors of one or two seconds relative to UTC.  None of this is a problem for administrative scope.  There is only one important thing to remember:

• The various machines may be several seconds out of synchronization.  Don't get upset if a door monitoring system reports that a door is opened several seconds before a different system reports unlocking the door.  It just means the two systems have a several second phase error.

Other than reminding the programmers to tolerate these phase errors there is nothing much to do.

The situation is rather different if you need to provide an operating room scope of phase and frequency error.  SNTP will never achieve this.  It simply jumps time whenever it wants to make an adjustment.  This breaks the frequency error limit.  SNTP also tolerates phase errors larger than the operating room tolerance.

There are two basic approaches to providing operating room scope for data gathering while using Windows:

1. Get time from something else.  There is no medical requirement that the time source used to get time stamps for medical data come from the operating system.  It is just as valid to have a separate piece of hardware provide the time.  Systems like the IRIG time synchronizing system are frequently used to synchronize data gathering equipment.  It can provide the time, and this time will be just as good for operating room scope.  It will need to be initialized by something with a time from an administrative scope, so it will be within a few seconds of UTC.
2. Replace the SNTP software and clock drivers with NTP software and clock drivers.  The PC hardware is capable of operating room accuracy.  It is the SNTP software and clock drivers that lack the accuracy.

I can't make any particular recommendations of which approach to use or any vendors.  I know of multiple vendors and I have seen a variety of different approaches deliver the necessary accuracy for operating room scope.