paul wrote: > > Hi David, I am wondering is there any other means to profile NTP > performance, like some kind of hardware setup to measure time offset > of two machine?
You need access to the source code of the clock interrupt service routine and the ability to directly right to something like a parallel port if you want to measure the true offset (relative to something like GPS pulse per second). The former, at least, you are not going to get under a closed source OS, like WINNT. Also remember that Windows never gives the time to application programs to better than 1ms, and this can degrade to more like 16ms. Also Windows offers no guarantees of scheduling latencies between real external events and when application code runs to service them. Another option might be to install some sort of clock card that can be read through a low latency device driver, but then you would be better using that synchronised clock card, rather than the software clock, for your timing. Although you might be able to drive a real (non-USB) parallel port, from application code, with fairly low latency the results would only be meaningful for a very unloaded machine, as, on a loaded machine, you wouldn't really know where you where in the system tick interval, when you read the software time. I'd suggest, therefore, that you will need to write a device driver, for good accuracy, and be Microsoft or their subcontractor, for full accuracy. _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
