[time-nuts] Accurate timestamping on computers (previously: For mywhole life timezones have been weird)

David J Taylor david-taylor at blueyonder.co.uk
Sat Nov 3 09:18:52 UTC 2012


-----Original Message----- 
From: Sarah White
[]
Seeing as I'm in the process of installing a hardware refclock (trimble
thunderbolt connected via serial port) for my NTP, it is highly
problematic and potentially error-prone for microsoft's OS to touch the
bios hardware clock AT ALL.

I'm entertaining the notion of writing a kernel-mode hardware timestamp
/ PPSAPI driver to pull the signal off the 1 PPS port on the tbolt one
way or another.

I plan to do this on windows. This is something I want to attempt even
though the NT kernel doesn't have the best reputation for realtime
hardware / interrupt handling. Plan is to put in a non-zero amount of
work, up to and including steps where I go through the driver signing
run-around with microsoft to actually have it fully recognized by the OS
without modification. (unless budget issues are a limiting factor)
[]
========================================

Sarah,

I don't know which version of Windows you are proposing to use, but I have 
NTP stratum-1 servers based on GPS devices with a PPS signal on the DCD line 
of the COM port, and Windows altering, or not altering, the hardware clock 
has /no effect/ at all.  I'm using Dave Hart's serialPPS.sys device driver 
on Windows-2000 up to Windows-7/64 (including telling Win-7/64 to ignore the 
signed 64-bit driver requirement).

GPS hardware:
  http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm
  http://www.satsignal.eu/ntp/Sure-GPS.htm

Windows stratum-1 notes:
  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html

I would note that for the best performance on a stratum-1 server you may 
want to try FreeBSD or even Linux on a Raspberry Pi.
  http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm
  http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

If Dave Hart's driver suits your needs, I'm sure he would be interested in 
getting it signed for Microsoft use (if he hasn't already done so).

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 





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