clock too slow - big time offset with ntpdate

[Ian Smith]

On Wed, 2 May 2007, Martin Dieringer wrote:
 [chomping, ccs too]
 > >> > >>> I get about half a second time offsets after 10 seconds, and more
 > >> > >>> than 100s after half an hour or so.
 > >> > >>> I think it has to do with powerd, if I kill that, the time stays 
 > >> correct.
 > >> > >>> It happens both on a Compaq nc4000 and an IBM ThinkPad T42p laptop.

 > >> > > Another effect of the problem seems to be the intermittent sound
 > >> > > output. Playback is ok when powerd is killed.
 > >> > > When changing freq by sysctl, I still get hickups in sound, so this
 > >> > > would be no solution.
 > >> >
 > >> > the hiccups have reappeared, so they are not related to powerd.
 > >> >
 > >> > I still have 0.5 seconds time offsets after 10 minutes, on the
 > >> > thinkpad, without powerd...

 > >> I'm wondering if this might have to do with power_profile's settings of
 > >> hw.acpi.cpu.cx_lowest when moving from AC to battery power?
 > >
 > > I don't have these values, are they ACPI?
 > > I switched off ACPI on both machines, but I use APM.

Ah, silly me, yes assuming ACPI.  powerd doesn't run on my Compaq 1500c
5.5-STABLE on APM, providing no dev.cpu.0.freq or dev.cpu.0.freq_levels
(though its APM BIOS provides working selectable half-speed on battery)

 > Might this have to do with it?
 > Now I got following while playing sound on the Compaq:
 > 
 > kernel: calcru: runtime went backwards from 183711700 usec to 183167434 usec for pid 12 (swi4: clock sio)
 > 
 > here I have a working clock, but also intermittent sound output

http://www.freebsd.org/doc/en/books/faq/book.html#CALCRU-NEGATIVE
 and
http://lists.freebsd.org/pipermail/freebsd-stable/ searching for
'calcru: runtime went backwards' provides many hits, as does google; 
seems it could be a number of things, perhaps choice of timecounter.

Out of my depth, Ian