"Evandro Menezes" <evan...@mailinator.com> wrote in message
news:2dd44831-09a6-4cf5-ac15-acc8ef6b0...@t20g2000yqa.googlegroups.com...
[]
Yes, except that Windows ends up raising the effective priority of
system tasks that supersede NTP's effective priority. Among the worst
offenders, network DPCs and some disk DPCs with some anti-virus
programs (i.e., Mcafee).
Then, even tasks with real-time priority will and do get starved and
an algorithm like NTP's, which has hard deadlines, suffers, thus the
inherently higher jitter in Windows.
Thanks, Evandro.
That could explain why I see higher NTP jitter on a Windows system running
a USB network source (digital video data stream) than receiving a similar
data stream on a PCI card under either Windows XP or Windows-7. I guess
it will depend on how well the DVB network component is written. This is
comparing PC Gemini (graph scale +/- 100ms) compared to PC Hydra (graph
scale +/- 3ms) here:
http://www.satsignal.eu/mrtg/performance_ntp.php
(BTW: I can't use the PCI card in the Vista system as the ASUS A8N SLI
deluxe motherboard will, apparently, blow power tracks if the PCI card is
used. I don't propose to test that!).
Having said that, anyone with such time-critical requirements will want to
stop all non-essential and any unpredictable processes such as anti-virus
or system updates and virus scans. On Windows-7 that can be quite a
challenge compared to Windows XP.
Cheers,
David
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