System clock is slow

Conrad Meyer cem at
Tue Mar 10 17:34:00 UTC 2020

On Tue, Mar 10, 2020 at 9:24 AM Theron <theron.tarigo at> wrote:
> I had previously used powerd to let the CPU underclock to 700MHz when
> idle.  Now, I've lost all control over CPU frequency (either by powerd
> or by sysctl) since there is some in-kernel cpufreq driver which I can't
> figure out how to disable.

It's hwpstate_intel(4).  You can add
'hint.hwpstate_intel.0.disabled="1"' in loader.conf or device.hints to
disable and use est(4), if you prefer.

The idea of the device is that hardware can do a better job managing
the frequency / power states rapidly than daemons like powerd.  But if
you like powerd/est, feel free to disable it.  Future models of Intel
CPU may not provide est(4).

If you leave it enabled, you can control the energy efficiency /
performance trade-off of hwpstate_intel on a per-core basis (or
per-package, if not disabled and hardware supports package-level
control) with 'dev.hwpstate_intel.<cpu>.epp=0-100' (sysctl or
tunable); the CPU uses this knob to control how biased it is towards
low frequency states.  100 is most efficient, 0 is most performant.
The default is 50.


More information about the freebsd-current mailing list