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Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management.Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. See Arch Linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time, e.g., arithmetic stuff, but not true for all tasks, e.g., loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on [Google+],(dead link)2:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on [Google+],(dead link)2:

• intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
• The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
• Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
• The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
• intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.