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[Solved] Cannot get overclocked frequency with i7/3930K
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corrosif
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Joined: 21 Dec 2003
Posts: 177
Location: France

PostPosted: Sun Feb 17, 2013 9:59 pm    Post subject: [Solved] Cannot get overclocked frequency with i7/3930K Reply with quote

Hi,

I have an Asus P9X79 motherboard with Intel Core i7 3930K processor.
Its stock frequency is 3.2GHz... however, I overclocked it without problem at 4.3GHz.

Here is my problem:
In Windows, by using CPU-Z, I get a report that my processor is effectly working at 4.3GHz.
In Gentoo Linux, it seems stuck at the stock frequency of 3.2GHz.

I have configured my kernel with following options:

Code:
CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_TABLE=m
CONFIG_CPU_FREQ_STAT=m
CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=m
CONFIG_CPU_FREQ_GOV_USERSPACE=m
CONFIG_CPU_FREQ_GOV_ONDEMAND=m
CONFIG_CPU_FREQ_GOV_CONSERVATIVE=m

CONFIG_X86_PCC_CPUFREQ=m
CONFIG_X86_ACPI_CPUFREQ=m


The performance governor should ensure that it stays at the highest possible frequency.
Even during a heavy multicore compilation, the content of /proc/cpuinfo always reports me the following:

Code:
cpu MHz         : 3201.000
bogomips        : 6400.23


And more puzzling... the file /sys/devices/system/cpu/cpu4/cpufreq/scaling_available_frequencies does not report my new overclocked frequency:

Code:
3201000 3200000 3000000 2800000 2600000 2400000 2200000 2000000 1800000 1600000 1400000 1200000


The governor seems to be set to right value, as stated by the file /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor:

Code:
performance


Please note that I have not emerged sys-power/cpufreqd yet (but I may try if you think that could help...).
What should I do, so that my kernel recognizes the overclocked 4.3GHz frequency I have set in the BIOS?
_________________
S'il n'y a pas de solution, alors il n'y a pas de problème (logique Shadok).


Last edited by corrosif on Wed Feb 20, 2013 10:58 pm; edited 1 time in total
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jathlon
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Joined: 26 Sep 2006
Posts: 89
Location: Canada

PostPosted: Tue Feb 19, 2013 9:52 am    Post subject: Reply with quote

This page explains the situation better than I can;

http://technicallyliving.blogspot.ca/2012/06/intel-turboboost-and-linux.html

joe
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corrosif
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Joined: 21 Dec 2003
Posts: 177
Location: France

PostPosted: Wed Feb 20, 2013 10:57 pm    Post subject: Reply with quote

Thanks for linking that page... excellent reading in fact!
For the ones passing by, and wanting to know how to ensure at which frequency the CPU is really working at, here is exactly what I made and discovered (I completed with some more informations I gathered from the web):

I reconfigured my kernel, activating following options:

Code:
CONFIG_X86_MSR=y
CONFIG_DEBUG_KERNEL=y
CONFIG_TIMER_STATS=y


As root, I compiled the tool turbostat present in the kernel:

Code:
cd /usr/src/linux/tools/power/x86/turbostat
make


And then, still as root, I ran it while compiling a big thing like LibreOffice in multi-core mode:

Code:
./turbostat

cor CPU    %c0  GHz  TSC    %c1    %c3    %c6    %c7   %pc2   %pc3   %pc6   %pc7
         91.87 4.30 3.20   7.64   0.24   0.00   0.25   0.00   0.00   0.00   0.00
  0   0  89.09 4.30 3.20  10.38   0.32   0.00   0.21   0.00   0.00   0.00   0.00
  0   6  93.47 4.30 3.20   6.00
  1   1  88.22 4.30 3.20  10.93   0.28   0.02   0.55
  1   7  95.45 4.30 3.20   3.69
  2   2  96.59 4.30 3.20   3.15   0.14   0.00   0.12
  2   8  89.98 4.30 3.20   9.76
  3   3  94.30 4.30 3.20   5.17   0.26   0.00   0.27
  3   9  90.92 4.30 3.20   8.55
  4   4  91.59 4.30 3.20   8.32   0.06   0.00   0.03
  4  10  90.15 4.30 3.20   9.76
  5   5  90.45 4.30 3.20   8.88   0.37   0.00   0.29
  5  11  92.27 4.30 3.20   7.06


- "%c0": percent of the interval that the CPU treated instructions (can be seen as the current "load" on the CPU, here heavily working on a compilation).
- "GHz": average clock rate while the core was in operating state.
- "TSC": frequency is the nominalmaximum frequency of the processor if turbo-mode were not available.

As seen in the column GHz, my processor is effectively working at 4.3GHz in Linux... which makes me happy :)

Also take notice that when the processor reaches a temperature above the processor TDP, Intel Power Boost may automatically adjust the frequency to lower values.

Thanks for the help!
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platojones
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Joined: 23 Oct 2002
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PostPosted: Thu Feb 21, 2013 1:23 am    Post subject: Reply with quote

There's also a tool in portage, called app-benchmarks/i7z, that gives you pretty much the same information, if you want to install it the gentoo way.
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corrosif
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Joined: 21 Dec 2003
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PostPosted: Thu Feb 21, 2013 2:24 am    Post subject: Reply with quote

i7z works great, thanks... very handy to have such a tool directly in portage :)
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