[SOLVED] speed of my cpu's in my laptop
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  1. #1
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    speed of my cpu's in my laptop

    I typed the following to get my cpu speed in my laptop:
    grep "cpu MHz" /proc/cpuinfo

    and got:
    cpu MHz : 1877.391
    cpu MHz : 1876.647
    cpu MHz : 1521.911
    cpu MHz : 1901.727

    But the same file /proc/cpuinfo
    also tells the cpu's speed:

    model name : Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz

    I have a few questions
    1) How do I know what speed my cpu's running
    2) Which speed my cpu's supposed to run at? I would think 2.50GHz,
    3) if my thinking correct, 2.5GHz. Then what made them running at different speeds: 1521.911MHz to 1901.727MHz
    way below 2500MHz
    4) Is there a program that we could set the speeds?

    Thank you in advance

  2. #2
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    Re: speed of my cpu's in my laptop

    You have a quad core. The CPU can run at 2.5 Mhz if three cores are turned off. Please measure with 1 core active, then 2 cores, etc.

    I would say, from your posting, that your system is healthy, with all quad cores active.
    Leslie in Montreal

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    http://forums.fedoraforum.org/showth...40#post1697840

  3. #3
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    Re: speed of my cpu's in my laptop

    Thank you, Isatenstein, for the reply.

    how about
    3) if my thinking correct, 2.5GHz. Then what made them running at different speeds: 1521.911MHz to 1901.727MHz
    way below 2500MHz
    4) Is there a program that we could set the speeds? Could we set them all run @ 2.5GHz?

  4. #4
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    Re: speed of my cpu's in my laptop

    Modern Intel cpu's control the frequency/voltage of each core dynamically and independently. The cpu driver in use is the intel_pstate driver. The default governor of this driver is the "powersave" governor. With almost no load on the cpu, the cpu cores will run at "idle" speed (lowest possible speed). They dynamically increase speed as needed, each core independently, up to the maximum rated speed (in your case 2.5Ghz). Also, if your cpu supports "turbo-boost", higher speeds are possible for individual cores unless all cores are already running at maximum speed. The speeds you see looking at /proc/cpuinfo are not static, they are merely a snapshot of the core speeds at the time you looked at them.

    Install the package "kernel-tools". Then, run as root,
    Code:
    # cpupower -c all frequency-info
    You cannot set a specific static speed. You can switch to the "performance" governor with the intel_pstate driver though.

  5. #5
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    Re: speed of my cpu's in my laptop

    Thank you, PabloTwo, That is what I am looking for

  6. #6
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    Re: speed of my cpu's in my laptop

    now I set the CPU speed as root:
    cpupower -c all frequency-set -g performance

    and I got
    grep "cpu MHz" /proc/cpuinfo
    cpu MHz : 2993.297
    cpu MHz : 3016.832
    cpu MHz : 3053.613
    cpu MHz : 2829.712

    Thank you folks

  7. #7
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    why cpu speed kept changing, in my laptop

    I noticed a very interesting behavior of my laptop, Dell Latitude
    I use
    grep "cpu MHz" /proc/cpuinfo
    to see my cpu speeds

    here are what I got

    when I first boot it up
    I had
    cpu MHz : 1574.778
    cpu MHz : 929.497
    cpu MHz : 944.785
    cpu MHz : 954.349

    then about a hour later
    cpu MHz : 802.811
    cpu MHz : 823.723
    cpu MHz : 799.027
    cpu MHz : 799.481

    then
    cpu MHz : 2993.358
    cpu MHz : 3030.396
    cpu MHz : 2993.323
    cpu MHz : 3004.024

    I did not do nothing with cpupower though, and I did not do anything, just browse the WEB, editing a word doc.

    Just don't know what caused those speed changes

  8. #8
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    Re: why cpu speed kept changing, in my laptop

    Your operating profile probably allows the OS to vary your CPU frequency based on load to reduce power consumption. This would be considered normal. You can look at /sys/devices/system/cpu/cpu[0-3]/cpufreq/scaling_governor to see the current configuration for each CPU #0 to #3. If it is set to ondemand, then the processor frequency will vary based on load. I typically force /sys/devices/system/cpu/cpufreq/ondemand/io_is_busy to 1 so I/O activity counts, and lower the up threshold to the minimum (11 last I checked) so it will go up faster and set the /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor to 40 for dropping back down.

  9. #9
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    Re: why cpu speed kept changing, in my laptop

    thank you, William, for the reply

    Learnt a lot

  10. #10
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    Re: why cpu speed kept changing, in my laptop

    mine actually just "powersave"

    Just as William mentioned

  11. #11
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    Re: speed of my cpu's in my laptop

    duplicate threads merged and moved to the appropriate forum section

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