El 23/01/2012 19:29, Chris Albertson escribió:
So back to time. If the goal is keeping good time then it is best
not to use Microsoft Windows. There are good technical reasons having
to do with the way MS Win. keeps and adjusts time. The bottom line is
that you will never be able to do better then about the millisecond
level even with a directly attached GPS. Using another OS, BSD or
Linux you can do almost three orders of magnitude better. (Three
orders is huge.) The OS and software is free and all you need is any
computer that has a physical serial port, not USB but a real DB9
connector. This is a good use for a 10 year old notebook PC. (The
computational load is trivial so even a 486 class computer is OK)
Hello,
I agree at all at not thinking on MS Windows for any precision timing
task (even low precision). We have some systems with a Windows based
workstation and Meinberg ntp distribution, and several linux embedded
processors taking the time from the workstation using ntp in a LAN (with
very very low traffic, also). This works well if you only need relative
precision (i.e. 1 second) time difference to the workstation, but once
we tried an application that required a synchronization between the
linux processors and the windows system in the order of 10ms, and this
never worked reliably. This is trivial to put into work in a LAN using
ntp or chrony. By orders of magnitude.
And that to not speak about the windows time server, not fully ntp
compatible but partially (to make things more confusing - the usual MS
way of taking an industry standard and pervert it on its own way -
rather imaginative also). You only need to have a look to this:
http://support.microsoft.com/kb/939322 amd particularly to the
paragraphs "We do not guarantee and we do not support the accuracy of
the W32Time service between nodes on a network" and "The W32Time service
cannot reliably maintain sync time to the range of 1 to 2 seconds". This
explains all...
Regards,
Javier
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