Something Wicked (with my hdwr clock) This Way Comes

Louis Lagendijk louis at lagendijk.xs4all.nl
Sat Dec 29 11:02:33 UTC 2007


On Fri, 2007-12-28 at 15:23 -0800, Dean S. Messing wrote:

> Jon, Aaron, I'd like to ask you both to run another test.  (Thanks in
> advance.)  As root, what does
> 
> adjtimex --utc --compare=20 --interval=10 > /tmp/adj_file.txt
> 
> give you? (It will take about 3.5 minutes for this to run)
> For the F7 machine on which I'm seeing the weird behaviour, 
> I get:
> 
> 
> [root at medulla ~]# adjtimex --utc --compare=20 --interval=10
>                                       --- current ---   -- suggested --
> cmos time     system-cmos  error_ppm   tick      freq    tick      freq
> 1198880050       0.798082
> 1198880059       0.900194    10211.2  10000  10426576
> 1198880069       0.002171   -89802.3  10000  10426576   10899   4022989
> 1198880078       0.104114    10194.3  10000  10426576    9899   4246426
> 1198880087       0.206065    10195.1  10000  10426576    9899   4194864
> 1198880096       0.308030    10196.5  10000  10426576    9899   4102676
> 1198880105       0.409981    10195.1  10000  10426576    9899   4193301
> 1198880114       0.511942    10196.1  10000  10426576    9899   4129239
> 1198880123       0.612893    10095.1  10000  10426576    9900   4192826
> 1198880132       0.714856    10196.3  10000  10426576    9899   4116739
> 1198880141       0.816836    10198.0  10000  10426576    9899   4002676
> 1198880150       0.918770    10193.4  10000  10426576    9899   4305801
> 1198880160       0.020729   -89804.1  10000  10426576   10899   4141739
> 1198880169       0.122682    10195.3  10000  10426576    9899   4180801
> 1198880178       0.224641    10195.9  10000  10426576    9899   4141739
> 1198880187       0.326589    10194.8  10000  10426576    9899   4213614
> 1198880196       0.428548    10195.9  10000  10426576    9899   4141739
> 1198880205       0.530505    10195.7  10000  10426576    9899   4155801
> 1198880214       0.632459    10195.4  10000  10426576    9899   4174551
> 1198880223       0.734426    10196.7  10000  10426576    9899   4088614

> I have no idea what's happening on my F7 system to cause the strange
> behaviour.  Does anyone else?
> 
> 
> Dean
> 
Could this be caused by some funny resolution of the system time
delivered by the RTC to the OS? If it delivers time only in seconds, by
uses some strange divider internally, one could see this
behaviour.....  
The RTC might still be accurate, but might vary upto one second from the
system clock.

Louis




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