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#1 2011-05-20 15:53:26

cavallino
Member
From: Campbell, CA
Registered: 2010-12-31
Posts: 14

speedstep and frequency scaling confusion.

I am using an overclocked i7 980x and I am getting some odd things surrounding frequency scaling. I am using a 134 fsb speed and x30 multiplier for 4010 ghz.

1. When using cpufreq utils only one core ever goes over 1596 and max 3326, that is the speed with the stock mutli and base clock value.
2. Without cpufrequtils the speed stays at 341x which is the stock multiplier and modded 134 base clock.
3. Without cpufrequtils I still seem to get temp drops at idle that are consistent with the downclocked speed. In windows 1604 idle usually results in temps around 26c and idle at max clock is usually 33c.


With that I have 2 queations

1. Does speedstep still work without cpufrequtils?
2. Is there anyway to fix the wrong mhz readings to ensure I am or am not getting the correct speed?

I am good at overclocking but is the first time I have used and overclocked cpu with Linux.

Last edited by cavallino (2011-05-20 17:43:31)

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#2 2011-05-20 19:29:09

James_Eder
Member
From: usa
Registered: 2011-05-19
Posts: 14

Re: speedstep and frequency scaling confusion.

Have you read over the wiki article?  https://wiki.archlinux.org/index.php/CP … cy_Scaling

cpufrequtils is not absolutely necessary, but it makes life easier and it doesn't hurt anything really.   It contains a daemon script to change the governor during boot and a few command-line utilities which assist in reading/writing to various parts of the /sys/devices/system/cpu/cpu*/cpufreq file system.

You may find the information you seek by typing:

$ cat /proc/cpuinfo

also

$ cpufreq-info -o

The functionality in the boot daemon is derived from cpufreq-set, so if you want to manually change governors and parameters after boot it's a good tool to have around.

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#3 2011-05-20 19:51:21

cavallino
Member
From: Campbell, CA
Registered: 2010-12-31
Posts: 14

Re: speedstep and frequency scaling confusion.

James_Eder wrote:

Have you read over the wiki article?  https://wiki.archlinux.org/index.php/CP … cy_Scaling

cpufrequtils is not absolutely necessary, but it makes life easier and it doesn't hurt anything really.   It contains a daemon script to change the governor during boot and a few command-line utilities which assist in reading/writing to various parts of the /sys/devices/system/cpu/cpu*/cpufreq file system.

You may find the information you seek by typing:

$ cat /proc/cpuinfo

also

$ cpufreq-info -o

The functionality in the boot daemon is derived from cpufreq-set, so if you want to manually change governors and parameters after boot it's a good tool to have around.

Yes I read the wiki but it seems to contradict the results.

The temperature never gets as low as it is getting without speedstep downclocking which makes it seem as if it is still working even without any daemons or modules loaded where as he wiki seems to imply that it will not work without them.

I use a script to watch proc/cpuinfo an that is where I am noticing the odd mhz readings and single core speed changes.

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#4 2011-05-20 21:15:15

James_Eder
Member
From: usa
Registered: 2011-05-19
Posts: 14

Re: speedstep and frequency scaling confusion.

Which governors are active while you're doing your testing?

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#5 2011-05-21 01:11:25

cavallino
Member
From: Campbell, CA
Registered: 2010-12-31
Posts: 14

Re: speedstep and frequency scaling confusion.

James_Eder wrote:

Which governors are active while you're doing your testing?

When using cpufrequtils I used the ondemand govenor. without cpufreq no govenors or modules loaded.

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#6 2011-05-21 02:24:10

cybertorture
Member
Registered: 2010-05-05
Posts: 339

Re: speedstep and frequency scaling confusion.

look here *points to short answer smile*


O' rly ? Ya rly Oo

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#7 2011-05-21 18:07:13

cavallino
Member
From: Campbell, CA
Registered: 2010-12-31
Posts: 14

Re: speedstep and frequency scaling confusion.

cybertorture wrote:

look here *points to short answer smile*

Ok so I guess it is just reading wrong then?

It still seems odd that only one core seems to change spedd is that the single core issue mentioned there?

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#8 2011-05-21 22:44:08

James_Eder
Member
From: usa
Registered: 2011-05-19
Posts: 14

Re: speedstep and frequency scaling confusion.

I guess you should try to make sure cpufreq scales correctly without overclocking first and then try it with your overclocking craziness.

It's been my experience that when changing the governor with cpufreq-set that you must do so for each core individually.  For example:

[james ~]$ cpufreq-info -o
          minimum CPU frequency  -  maximum CPU frequency  -  governor
CPU  0       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
CPU  1       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
CPU  2       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
CPU  3       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
[james ~]$ sudo cpufreq-set -g performance
[james ~]$ cpufreq-info -o
          minimum CPU frequency  -  maximum CPU frequency  -  governor
CPU  0       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  performance
CPU  1       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
CPU  2       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
CPU  3       800000 kHz ( 25 %)  -    3200000 kHz (100 %)  -  ondemand
[james ~]$

Note that only CPU 0 is changed.

There is a -r switch which is supposed to effect a change for all "related" processors but it doesn't seem to work the way one might expect. It often enough has no effect on any CPU other than CPU 0.

I ended up creating a script to hit each CPU individually.  A simplified version is:

#!/bin/bash
for i in {0..3}; do
  sudo /usr/bin/cpufreq-set -c $i -g ondemand
done

Of course one would have to change the 3 to represent the highest processor number in the system running it, but you get the idea.  If you want to do the same without the cpufrequtils package you can do something like:

#!/bin/bash
for i in {0..3}; do
  sudo sh -c "echo ondemand > /sys/devices/system/cpu/cpu$i/cpufreq/scaling_governor"
done

Although this could be less flexible and more fragile.

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#9 2011-05-21 23:28:18

cavallino
Member
From: Campbell, CA
Registered: 2010-12-31
Posts: 14

Re: speedstep and frequency scaling confusion.

Ok so further testing has revealed.

1. Multiple cores are scaling but using cpufreq-info it seems to only happen one thread a time. For example compiling something large with the flag to use all threads will show it rotating through cores going back and forth from 1.6 to 3.33.

Maybe it's normal? Usually my other arch boxes seemed to scale all threads/cores at once but maybe that was just because they are less powerful?

2. It does this at dead stock speeds too.

3. Regardless of what cpufreq is stated compile times at 4.01 are significantly faster than 3.33 so clearly it just stating the wrong number but is running at the right speed.

According to cpufreq-info -o all cores are set with the ondemand govenor.

Still none of this seems to explain why temps seemed to show it scaling before cpufreq or any governors were set. Does the mainline kernel do any native scaling on it's own without a driver or module loaded?

Last edited by cavallino (2011-05-21 23:29:58)

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