Kernel Variables Sanity Check

Gonzalo Nemmi gnemmi at
Wed Dec 24 11:24:16 UTC 2008

On Wednesday 24 December 2008 2:13:10 am Jason C. Wells wrote:
> Based on someone elses historical message I tried changing the time
> counter from TSC to i8254
> # sysctl kern.timecounter.hardware=i8254
> and after doing some manual calculations I tweaked
> # sysctl machdep.i8254_freq=1187216
> # machdep.i8254_freq: 1193182 -> 1187216
> Is doing this safe?  I'm concerned that there are unforeseen
> consequences to messing with these kernel variables.  Ntpd seems to like
> this setup.  Anything to make ntpd happy.
> And if I may, why can't ntpd do this? (Don't answer that.) I use the
> FINE software to set my clock so I don't have to.  It's supposed to make
> my life easier.
> Thanks,
> Jason

Hi Jason, and sorry to pop in, but now you got me guessing if I should follow 
your lead too ...

This is what I get in here:

[gonzalo at inferna ~]% grep Time /var/run/dmesg.boot
Timecounter "i8254" frequency 1193182 Hz quality 0
Timecounter "ACPI-safe" frequency 3579545 Hz quality 850
acpi_hpet0: <High Precision Event Timer> iomem 0xfed00000-0xfed003ff on acpi0
Timecounter "HPET" frequency 14318180 Hz quality 900
Timecounters tick every 1.000 msec

Should I change kern.timecounter.hardware to i8254 too??

Gonzalo Nemmi

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