Hello, I have an ASUS P8Z77-V motherboard with an i7 3770k. I overclocked the CPU in the BIOS utilizing P states to get it up to 4.4 GHz. In Windows, normally it runs at 3.5GHz but under load it revs up to 4.4 (CPU-Z). Running cat /proc/cpuinfo while ripping a DVD with Handbrake, Linux reports that it only hits 3.5 GHz maximum.

In the kernel I enabled the acpi-cpufreq module for Intel SpeedStep and I set the CPU frequency scaling governor to userspace, but when I try to set the maximum CPU frequency to 4.4 GHz the file reverts back to 3.5 GHz. Same thing happens when I try to set the current CPU frequency.

I installed i7z and it is also reporting the CPU running at 3.5 GHz.

As a final test, I launched Windows 7 in a Virtualbox instance, installed CPU-Z, and it also reported a maximum speed of 3.5 GHz.

How can I be sure if Linux is utilizing my overclocked CPU to its full potential? Thanks.

Have you tried cpupower? It's the replacement for cpufreq-utils. More Gentoo info here.

Alex Brinister

I had assumed that i7z would give me accurate processor frequency data but I'll try this as well. Thanks.

I did too (when I first started using i7z). Turns out, I had to use cpupower to actually set the correct frequency and then i7z would give me the correct value. I could not do this in my BIOS because it has no support. I'm stuck with userspace tools :/.

Alex Brinister

Thank you, it works! I used cpufrequtils since it was already in the repo, ran this:

for i in {0..7}; do cpufreq-set -c $i -u 4.4GHz; done

and noticed that all cores in i7z are now hitting the max multiplier of 44 when I rip a movie with Handbrake.

EDIT:
after creating a script to run this at boot, I noticed the CPU still had the hard limit of 3.5GHz. The fix seems to be this:

#!/bin/bash
for i in {0..7}; do echo "4400000" > /sys/devices/system/cpu/cpu$i/cpufreq/scaling_setspeed; done
for i in {0..7}; do /usr/bin/cpufreq-set -c $i -u 4.4GHz; done

Weird, maybe that's why they recommend cpupower...

Glad I could help. I only mentioned cpupower because Arch has deemed cpufrequtils out of date. So I switched over to cpupower. They have virtually the same function.

Alex Brinister