Weird rtc interrupt rate

Hi,

I have a Dell Latitude CPx laptop running FreeBSD 5.2-CURRENT.  I have
been using FreeBSD on this laptop for a long time, and the problem I'm
going to describe also happened while it was running 4.6-STABLE.

Sometimes, when wathing at my processes using top(1), all CPU states
are 0.00.  Since ps(1) shows the same behaviour, this is not a bug in
top(1).  But when this problem happens (this seems to be completly
random), vmstat(8) shows a weird interrupt rate for rtc :

# z6po:root# vmstat -i | sed -n '1p; /rtc/p;'
# interrupt                          total       rate
# irq8: rtc                        7584528        115

or, two hours later, while the computer was 100% idle :

# z6po:tataz$ vmstat -i | sed -n '1p; /rtc/p;'
# interrupt                          total       rate
# irq8: rtc                        7584528        101

AFAIK, rtc interrupts rate should be something like 127 or 128.  What
could make the rate being so unstable ?

(I'm not a kernel nor hardware guru, so I may have forget to give
revelant informations.  Please ask me if you want more informations.)

Regards,
-- 
Jeremie LE HEN aka TtZ/TataZ                          jeremie.le-hen_at_epita.fr
                                                                 ttz_at_epita.fr
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