Hi
DPC Latency = Deferred Procedure Call Latency = how long it takes
Windows to get around to doing what it should do real time. Put another
way - how lazy is your computer?
It may not be a big issue, but it's probably worth checking for free:
http://www.thesycon.de/deu/latency_check.shtml
We don't do audio or video since we're serious Time Nuts:)... The same
issue would mess up our stuff though. It certainly would be useful to
know when playing with NTP.
Usual disclaimer - if your PC explodes don't blame me. There are lots of
other programs out there that do the same thing. I have no connection
with these guys. It's just the first one I found.
Bob
Bob,
Yes, that's a program which produces some interesting results, and has
been useful for detecting bad behaviour by some poorly written drivers
(e.g. when receiving masses of data over a satellite DVB link).
For NTP, I think you may find that all the time-critical stuff is done at
high-priority, and it's only the non-time critical stuff which is done at
DPC time. This is how the DPC is intended to be used, of course. VMS has
a similar mechanism, ASTs, if I recall correctly, but that was a long time
ago.
On Windows with NTP, you can get within a couple of hundred microseconds
(XP) or perhaps 50 microseconds (Windows-7) if my graphs here are any
guide:
http://www.satsignal.eu/mrtg/performance_ntp.php
The best I can offer is within 10 microseconds or so on an Intel Atom
system running FreeBSD. I'm sure that others can do better!
Cheers,
David
--
SatSignal software - quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
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