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Old 04-09-2007, 01:24 PM   #1
cwej
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Recognized CPU less than advertised


This may just be a dumb question. I have a IBM T41 laptop that claims to have a 1.6 ghz processor. However, it seems to be running at 600Mhz, rather than 1.6Ghz.

I didn't notice this until I changed desktop to Kubuntu which defaults loading a CPU frequency applet on the panel.

When I run "cat /proc/cpuinfo" it indeed shows "Model name: Intel(R)Pentium (R) M processor 1600MHZ"; and then "cpu Mhz: 600.000"

My performance is actually quite good, better than when it was formerly operating under Windows (presumably operating at full 1.6 Ghz speed?).

Is there some glitch that is causing GNU/Linux (or Ubuntu 6.10) to cut the cpu speed, or is there something that I just don't understand?

Any insights would be appreciated.
 
Old 04-09-2007, 01:51 PM   #2
spaaarky21
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Quote:
Originally Posted by cwej
When I run "cat /proc/cpuinfo" it indeed shows "Model name: Intel(R)Pentium (R) M processor 1600MHZ"; and then "cpu Mhz: 600.000"
I noticed the same thing when running Fedora Core 3 on my Compaq laptop. I believe this has to do with CPU performance scaling. Your laptop is running slower to save power when it is not under a heavy load. Try getting the CPU usage up and try again. Hopefully the CPU clock speed will be greater... or maybe not. I don't know that my clock speed ever increased according to /proc/cpuinfo but everything runs faster with FC3 than it did with Windows so I never worried about it too much.

-Brandon R
 
Old 04-09-2007, 03:26 PM   #3
cseanburns
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I had the same issue with my laptop and found a nice app for controlling CPU speeds. It's called 'cpufrequtils' and it's available via apt-get.

The two commands you'll need that come with this package are called 'cpufreq-set' and 'cpufreq-info'.

Read the manpages for each. You can temporarily set the cpu frequency by issuing the following command:

> sudo cpufreq-set -f 1600000

Which would set the cpu to 1.6 GHz. Or you can set the governor or policy that controls performance to maximum; this way it will remain at the highest frequency (until reboot, that is).

> sudo cpufreq-set -g performance

Here's the site for cpufreq-utils:

http://www.kernel.org/pub/linux/util...frequtils.html
 
Old 04-09-2007, 04:05 PM   #4
spaaarky21
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Quote:
Originally Posted by cseanburns
I had the same issue with my laptop and found a nice app for controlling CPU speeds. It's called 'cpufrequtils' and it's available via apt-get.
Sounds neat. But did it kill your battery life?

-Brandon
 
Old 04-09-2007, 04:13 PM   #5
cseanburns
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Well, it's an older laptop and the battery charge is less than half its original potential so I don't use it on battery power much these days, but yeah, it will decrease your battery charge much more quickly than if not setting it. But if you're not getting the cpu power you need when you laptop is plugged in, it's definitely useful.

However, the cpufrequtils package lets you control everything, so if you wanted, you can set the governor (policy) to powersave rather than performance when you're running off battery power.
 
Old 04-09-2007, 04:25 PM   #6
ErrorBound
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As others have said, linux is scaling down the cpu frequency to save your battery when it is under low load. Try compiling and running something simple like
Code:
#include <iostream>

int main()
{
  int i;

  while(1)
    {
      i++;
    }
}
which will give the processor something to do. Now do 'cat /proc/cpuinfo' again (in another terminal), and see that it is now running at full speed. Cool eh? This will keep running until you stop it by doing ctrl+C.
 
Old 04-09-2007, 05:08 PM   #7
cavalier
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My HP zv5320us does something similar. It's an AMD CPU, and it's supposed to run at 1.6, but most of the time idles along at 800MHz. I put on gdesklets and put on a CPU monitor, and I can watch it jump to 1.6 when the need arsies.

What has me concerned about yours is that 600MHz is a really odd fraction of 1.6GHz...
 
  


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