[ntp:questions] Windows timekeeping - sudden degradation - why?

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Sun Dec 4 10:40:07 UTC 2005


I run a number of NTP systems based on Windows, and normally all but the 
Windows 2000 Workstation keep good time.  In particular, the Windows XP 
SP2 system kept good time until about 14:00 UTC on Friday 2nd December.


I asked myself what changed on the system and, as far as I know, the 
answer is nothing!  Around that time, I was developing a program for 
processing large images, and fed it an image which was too large.  Perhaps 
coincidental - perhaps not.  The pagefile size is fixed at 2GB and seems 
to still be the same.  I wondered if disk I/O had become switched from 
UDMA to PIO, but its seems not.  I've checked for spyware and neither 
SpyBot nor AdAware find anything other than cookies.  I don't see anything 
unusual in Services.  I even did a system restore to around 12:58 (IIRC) 
on the day in question, but this didn't cure the problem.

I'm stuck!  Can you help?  Why would an otherwise good timekeeper become 
degraded in this way?  The jitter figures (from ntpq -p) are in the 10 - 
15 millisecond range, even for servers on the LAN, whereas other PCs on 
the same LAN show jitter under a millisecond.  Lan traffic looks normal, 
though.  The delay figures look normal as well.

Any ideas?  (no, replacing XP is not an option!).


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