Tuning Power Consumption on FreeBSD Laptops and Intel Speed Shift (6th Gen and Later)

When running FreeBSD on laptops with a 6th Gen (Skylake) or later Intel CPU, for me these are HP Spectre x360s (sorry, I’m not a ThinkPad fan), one annoyance with the out of the box FreeBSD configuration is the fact that the fan is running most of the time.

In comparison, a HP Envy with an AMD Ryzen does not have this issue with an out-of-the-box FreeBSD.

One thing that Intel has done with these modern CPUs is include a technology called Speed Shift. While Windows and Linux may have configurations that automatically optimize for computers with batteries or without, FreeBSD’s default Speed Shift configuration is more optimized for computers without a battery. Meaning it attempts a “balance” between “performance” and “power consumption”, but this also means the Spectre’s fan is always running.

Fortunately, this can be tuned, as per the hwpstate_intel man page.

In short, what you need is this in your /etc/sysctl.conf:


Where N is the number of threads minus one.

In case you were wondering, the 100 is actually a value between 0 (best performance) or 100 (most power savings). The default is 50 which attempts a balance, but I set it to 100 for laptops.

For me, I have a 4-core, 8-thread Intel Core i7-1165G7 in my Spectre x360 14", and the respective /etc/sysctl.conf entry is:


You can either “reboot” (easier for me), or do sysctl dev.hwpstate_intel.0-N.epp=100 manually if you want it done right away.

And enjoy the fan not running all the time! The fan will still run, but less frequently than it did earlier.