Upgrading to 6.X there's a mention in the release notes for CPU scaling configuration for Haswell and Ivy Bridge processors.

 

http://lime-technology.com/wiki/index.php/Upgrading_to_UnRAID_v6

 

More Tips

• CPU speed and power saving workaround
  • The newer Linux kernels have automatic CPU frequency step down when more CPU speed is not needed, saving power and heat. But, if your CPU is an Intel Haswell or possibly an Ivy Bridge, including most Xeon's, then there is a frequency scaling issue with the intel_pstate driver, and it needs to be disabled.
  • It's nothing serious, just means the CPU won't power down to lower frequencies when idle, so you may pay a little more in power costs. It will not hurt you in any other way.
  • To regain the CPU frequency stepping down, there are several things you can do.
    • You can install the Tips and Tweaks plugin and change the CPU Scaling Governor.
    • You can edit syslinux/syslinux.cfg on the flash drive, and insert intel_pstate=disable in the append lines.
    • Easy way to edit syslinux.cfg - browse to your unRAID Main screen, click on your Flash drive, and drop down to the Syslinux Configuration section! Make sure you click on the Apply button.
    • You will want to change these:

    append initrd=/bzroot

    append initrd=/bzroot unraidsafemode

    • To these:

    append intel_pstate=disable initrd=/bzroot

    append intel_pstate=disable initrd=/bzroot unraidsafemode

    • You can monitor the current CPU frequency for each core on the Dashboard.

 

What's not stated in the first bullet is what selection to change the CPU Scaling Governor to?  Choices are:  OnDemand, PowerSave, Conservative, Performance, Scheduled.   Which would be the correct selection for the intent?

Edited May 3, 20179 yr by joedotmac

I use an Ivy Bridge CPU but never saw this on my machine...

What is this? A bug?

I just upgraded to an i7 10700k CPU and was having issues with heat compared to my previous Xeon.  I followed some threads like this and found that the CPU was never stepping down to a lower frequency (it was always running the cores at 4.7GHz).  I added the intel_pstate=disable flag and then set the tips & tweaks CPU governor setting to 'on demand".  Voila!  The CPU frequency now steps up and down depending on CPU load and my fans are a lot more calm.

 

Thanks for your post!

This guide also fixed my issue on an Intel NUC NUC10i5FNB with an Intel Core i5-10210U CPU (Unraid 6.10.3)

I changed the CPU Scaling Governor to Conservative with the Tips and Tweaks Addon.

 

Thank you for the post!

I wanted to disable intel_pstate for switching to acpi_cpufreq to save some power. But after some search, i realized that the 'powersave' governor is roughly the equivalent 'ondemand' in acpi_cpufreq. 

Previously when my server is idling, cpu mostly stays at 4.1GHz and cpu temperature is over 40C. (room temperature 20C)

After switched to 'powersave' governor, the frequencies now scales dynamically, cpu temperature mostly stays around 35-36C.

For those only wanted to switch to acpi_cpufreq for 'ondemand', you can just set to 'powersave' in intel_pstate driver no need to change to acpi driver.  ( the 'powersave' from acpi driver will set your cpu to the lowest frequency static, it is quite different!)

Btw, notice for HP servers, if you want to disable intel_pstate you probably need to disable CPC (collaborative power control) from RBSU/Bios but it will going to be changing some other related power configs.  (I tried 'intel_pstate=disabe' but it didn't bring me to acpi_cpufreq driver after rebooting.) So i decided to stay with intel_pstate

Anyway, still thanks to Joedotmac for the steps above