Windows 7: What is meaning of Min/Max CPU in Power settings?

MeepMeep · 02 Aug 2012

I see settings for Min Cpu and Max Cpu, which are percentages. But percentages of what value?
I would like to use these settings to have the computer run always (unless it gets overheated) at the P0 P-State, so that the RDTSC instruction consistently reflects time in clock cycles. But I don't know if 100% means the P0 frequency, or the fastest boosted P-State frequency, or something else altogether.
Also, does anybody have a tool or some other way to see what all the normal and boosted P-States are on my system? I suppose I can read write a program to read the MSRs (I have a kernel mode driver to facilitate this), but I'm lazy.
Thanks for any help.

**centaur78** · 02 Aug 2012

Minimum Processor state : Specifies the minimum processor performance state. The performance state is specified as a percentage of maximum processor frequency.

Maximum Processor state : Specifies the maximum processor performance state. The performance state is specified as a percentage of maximum processor frequency.

logicearth · 02 Aug 2012

See SpeedStep for Intel processors, Cool'n'Quiet for AMD processors. You can see the affect of these settings with Resource Monitor, CPU panel labeled as "Maximum Frequency" at the top.

MeepMeep · 03 Aug 2012

Quote: Originally Posted by centaur78

maximum processor frequency.

I don't know what my maximum frequency is. I have made a table that matches values of Minimum with resulting clock rates with an idle computer. The results are:

0% - 45% = 1.4 GHz
46% - 61% = 1.9 GHz
62% - 74% = 2.3 GHz
75% - 90% = 2.8 GHz
91% - 100% = 3.4 GHz / 4.0 GHz (depending on load)

My boosted P-State seems to be 4.0 GHz. That's what it runs at when the core has been active for awhile.

The TSC appears to be running at a constant 3.1 GHz. The first four speeds are the indicated % of 3.1 GHz, or very nearly.

For the Maximum setting, the clock rates when the core is busy are:

0% - 60% = 1.4 GHz
61% - 73% = 1.9 GHz
74% - 89% = 2.3 GHz
90% - 99% = 2.8 GHz
100% = 3.4 GHz / 4.0 GHz (depending on load)

So I think the answer is this: Each P-State frequency is converted to a % of the P0 frequency, and boosted states are set at 100%. Any P-State is available to be used if Min % <= P-State % <= Max Pct. Windows will come up with something reasonable (and not crash) if none of the P-States qualifies. And it doesn't seem that Windows actually uses P0 when there are boosted P-States on the processor.

Do you guys concur with this?

Another related question:

Anybody know of a tool that lets me adjust other parameters, such as the actual P-State frequencies and voltages, or the policy for switching between them. Particularly, I'd like to alter the policy on just one core, where I'm running heavy stuff, and leave the others normal.

Thanks.

**centaur78** · 04 Aug 2012

Hi

First off to check your processor max frequency, you can use CPU-Z or even good old System properties to tell you what the frequency is. Eg: if it says Intel Core 2 Duo @ 2.00 GHz.... thats you max frequency for each core ....

There are several tools to test and verify system PPM support.Below are some of them

• Windows Resource Monitor
This tool lets you view a quick summary of the processor usage versus the processor speed. This tool is included with Windows. eg

What is meaning of Min/Max CPU in Power settings?-performance-state-usage.png

• Windows Reliability and Performance Monitor
This tool lets you view a plot of the current speed of each processor core against the processor usage. It also provides logging and graphical display capabilities. This tool is included with Windows.eg

What is meaning of Min/Max CPU in Power settings?-performance-monitor.png

• Event Viewer
This tool lets you view entries in the system event log. The system event log includes entries that contain summary information about platform PPM capabilities and error messages that were logged when ACPI processor objects failed validation checks. This tool is included with Windows.

• PowerCfg
This command-line tool lets you view or change the processor power policy, including power policy values that are not exposed in the Control Panel Power Options application. This tool is included with Windows.

• Pwrtest
This command-line tool lets you view detailed information about system PPM capabilities and provides test and logging capabilities for multiple power management scenarios. This tool is included with the Windows Driver Kit (WDK).

To view supported PPM states .... use the command below.. This give you for each core of the processor --- the performance states and the idle states supported by the processor.

Code:

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Program Files (x86)\Windows Kits\8.0\Tools\x64>pwrtest /info:ppm


InstanceName: ACPI\GenuineIntel_-_Intel64_Family_6_Model_15_-_Intel(R)_Core(TM)2
_Duo_CPU_____T5750__@_2.00GHz\_0_0

Processor Performance States
  PerfStates:
    Max Transition Latency:  10 us
    Number of States:        12

    State  Speed (Mhz)    Type
    -----  ------------   ----
      0     2000 (100%)   Performance
      1     1667 ( 83%)   Performance
      2     1333 ( 66%)   Performance
      3     1000 ( 50%)   Performance
      4     1000 ( 50%)   Throttle
      5      870 ( 43%)   Throttle
      6      750 ( 37%)   Throttle
      7      620 ( 31%)   Throttle
      8      500 ( 25%)   Throttle
      9      370 ( 18%)   Throttle
      10     250 ( 12%)   Throttle
      11     120 (  6%)   Throttle


InstanceName: ACPI\GenuineIntel_-_Intel64_Family_6_Model_15_-_Intel(R)_Core(TM)2
_Duo_CPU_____T5750__@_2.00GHz\_1_0

Processor Performance States
  PerfStates:
    Max Transition Latency:  10 us
    Number of States:        12

    State  Speed (Mhz)    Type
    -----  ------------   ----
      0     2000 (100%)   Performance
      1     1667 ( 83%)   Performance
      2     1333 ( 66%)   Performance
      3     1000 ( 50%)   Performance
      4     1000 ( 50%)   Throttle
      5      870 ( 43%)   Throttle
      6      750 ( 37%)   Throttle
      7      620 ( 31%)   Throttle
      8      500 ( 25%)   Throttle
      9      370 ( 18%)   Throttle
      10     250 ( 12%)   Throttle
      11     120 (  6%)   Throttle


InstanceName: PPM_Processor_0

Kernel Idle States: (3 states)

  TargetState:       2
  Type:              0
  TargetProcessors:  0x1
  State 0:
    Latency:          1 us
    Power:            1000 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C1
    IdleHandler:      Present
    Context:          Present
  State 1:
    Latency:          1 us
    Power:            500 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C2
    IdleHandler:      Present
    Context:          Present
  State 2:
    Latency:          57 us
    Power:            100 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C3
    IdleHandler:      Present
    Context:          Present


InstanceName: PPM_Processor_1

Kernel Idle States: (3 states)

  TargetState:       2
  Type:              0
  TargetProcessors:  0x2
  State 0:
    Latency:          1 us
    Power:            1000 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C1
    IdleHandler:      Present
    Context:          Present
  State 1:
    Latency:          1 us
    Power:            500 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C2
    IdleHandler:      Present
    Context:          Present
  State 2:
    Latency:          57 us
    Power:            100 mWatts
    TimeCheck:        97414 QPC ticks (50 ms)
    PromotePercent:   10%
    DemotePercent:    5%
    StateType:        C3
    IdleHandler:      Present
    Context:          Present


C:\Program Files (x86)\Windows Kits\8.0\Tools\x64>

The below shows an example of the output of Pwrtest when it is run in sampling mode. Watch at 75000ms when i started running MSE... the idle states of each core are changed as well as the performance states and increased to cope up with the load ....

Code:

C:\Program Files (x86)\Windows Kits\8.0\Tools\x64>pwrtest /ppm
      Elapsed  Idle   C1   C2   C3  P-     Freq    Freq     Perf/
Cpu      [ms]   [%]  [%]  [%]  [%]  State   [%]   [MHz]  Throttle
---   -------  ----  ---  ---  ---  -----  ----   -----  --------
  0      4992    92    0    0  100      3    50    1000         P
  1      4992    88    0    0   99      3    50    1000         P
  0      9999    97    0    0  100      3    50    1000         P
  1      9999    96    0    0  100      3    50    1000         P
  0     14991    87    0    0  100      3    50    1000         P
  1     14991    82    0    0  100      3    50    1000         P
  0     19998    90    0    0  100      3    50    1000         P
  1     19998    90    0    0  100      3    50    1000         P
  0     24990    99    0    0  100      3    50    1000         P
  1     24990    98    0    0  100      3    50    1000         P
  0     29997    99    0    0  100      3    50    1000         P
  1     29997    97    0    0  100      3    50    1000         P
  0     34989    98    0    0  100      3    50    1000         P
  1     34989    98    0    0  100      3    50    1000         P
  0     39996    98    0    0  100      3    50    1000         P
  1     39996    99    0    0  100      3    50    1000         P
  0     44988    98    0    0  100      3    50    1000         P
  1     44988    98    0    0  100      3    50    1000         P
  0     49995    96    0    0  100      3    50    1000         P
  1     49995    98    0    0  100      3    50    1000         P
  0     55002    82    0    0  100      3    50    1000         P
  1     55002    83    0    0  100      3    50    1000         P
  0     59994    96    0    0  100      3    50    1000         P
  1     59994    98    0    0  100      3    50    1000         P
  0     65001    97    0    0  100      3    50    1000         P
  1     65001    97    0    0  100      3    50    1000         P
  0     69993    90    0    0  100      3    50    1000         P
  1     69993    85    0    0  100      3    50    1000         P
  0     75000    55    0    0   99      3    50    1000         P
  1     75000    34    3    8   87      3    50    1000         P
  0     79992    69    0    0  100      2    66    1333         P
  1     79992    26    1   11   87      2    66    1333         P
  0     84999    88    0    0  100      3    50    1000         P
  1     84999    62    2    4   93      3    50    1000         P
  0     89991    80    0    0  100      2    66    1333         P
  1     89991    30    1    6   91      2    66    1333         P
  0     94998    79    0    0  100      3    50    1000         P
  1     94998    49    1    3   95      3    50    1000         P
  0    100005    70    0    0  100      3    50    1000         P
  1    100005    33    0    3   96      3    50    1000         P
  0    104997    73    0    0  100      3    50    1000         P
  1    104997    45    0    7   92      3    50    1000         P
  0    110004    84    0    0  100      3    50    1000         P
  1    110004    47    0    1   98      3    50    1000         P
^C
C:\Program Files (x86)\Windows Kits\8.0\Tools\x64>

In another related question.... what you are trying to achieve is something called Core Parking. i have attached a doc for your reference.... most of what you want to achieve can be done through the registry by looking at the respective GUID
Core Parking.pdf

There is one other tool called Manage Parked CPU Utility you could also try .... but i am not sure wheather you could induvidually manage the core....since core parking works on certain class of multicore processors. just give it a try and let me know..

Windows 7: What is meaning of Min/Max CPU in Power settings?

What is meaning of Min/Max CPU in Power settings? problems?