[ntp:questions] NTP client with ability to write Windows NT system time to hardware clock?

Martin Burnicki martin.burnicki at meinberg.de
Tue Jan 4 09:43:01 UTC 2011


David J Taylor wrote:
> It would certainly be good to have kernel-mode timestamps in Win-64.
> Although the average jitter reduction achieved by switching from user-mode
> to kernel-mode is not great (say from 3.5 microseconds to 2.2
> microseconds), the greater consistency and freedom from jitter spikes may
> well be helpful.

Hm, I recently found that at least under Windows Server 2008 x64 the
QueryPerformanceCounter (QPC) call is obviously emulated when running 32
bit applications on this 64 bit system. 

My wclkres program (32 bit binary)
http://www.meinberg.de.www/download/utils/windows/wclkres-1.4.zip
reports a QPC frequency of 2.341 MHz and a thus a resolution of 427 ns only.
The mean execution time of a QPC call is about 64 ns, so subsequent QPC
calls often return the same values.

So maybe native 64 bit binaries would yield better results than 32 bit
binaries on an x64 system.


Regards,

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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