CPU frequency is always at minimum, even if CPU usage is 100%

It turned out that this problem was unrelated to the intel_pstate driver, because acpi_cpufreq, the other driver, reported better values but never set them. The OS had probably no control over this.

This is a issue that happens with certain Dell laptops when charging is broken in a way that the laptop is powered by AC but not charged. Fixing the hardware problem removes the problem. In this case, it was an almost invisible piece of cloth in the power connector that prevented electrical contact.

Sometimes my laptop completely ignores the cpufreq settings. I found this works:

Unplug the power cord and plug it back in again. Fixed :)

I am guessing the reason is that the machine got confused: it thinks it is on battery, and it thinks the battery is low, so it underclocks the CPU to save power.

We just need to let it know that it is actually plugged in and doing fine.

(Asus x453m laptop here, Ubuntu 14.04) YouTube: Have you tried turning it off and on again?

This will set your cpu freq to top speed from any terminal:

sudo cpufreq-set -f `cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq`

Edit the /etc/init.d/ondemand file to permanently add this. ondemand is used to modify your freq during login. The default is the 'ondemand' governor. In other words you start at 800mhz and go up as needed.