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Topic Title: Guide to Locking the CPU at Lowest Performance
Topic Summary: Minimizing heat & noise w/ Cool'n'Quiet
Created On: 03/29/2009 02:23 PM
Status: Read Only
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 03/29/2009 02:23 PM
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Posts: 1
Joined: 03/29/2009

CPU: Athlon 64 X2
Platform: Windows XP SP3
Driver: AMD Processor Driver

While watching streaming video with Cool'n'Quiet enabled I observed my CPU freq to be fluctuating between minimum (1.0 GHz) and maximum (2.8 GHz). The CPU was in turn running hotter than at minimum freq and the CPU fan, inaudible at minimum freq, was making considerable noise. I wanted to eliminate the extra fan noise.

I first determined that performance was sufficient at minimum CPU freq by locking the CPU freq at minimum in the BIOS and watching some streaming video. I then set about creating a convenient way to lock the CPU freq at minimum without requiring a reboot and entry into BIOS setup.

The solution was to user the Windows powercfg command line utility to create a new Windows power profile with the CPU throttling parameters set to CONSTANT.

Brief Instructions for Experts

From an account with administrative privileges, use powercfg in a Command Prompt window to perform the following steps.
The command "powercfg /?" displays the command usage.

1. Whatever Windows power profile you use for Cool'n'Quiet, make a new copy of that profile with a nice descriptive name.

2. In your newly created Windows power profile, change the AC and DC CPU throttling parameters from ADAPTIVE to CONSTANT.

That's it!

Detailed Instructions & Example

This example will use the Minimal Power Management power profile as a starting point, and will create a new power profile named "Minimal CPU Lowest".

1. Log in to an account with administrative privileges.

2. Open a Command Prompt window.

3. Ensure that Minimal Power Management is the active power profile with the following command:

> powercfg /s "Minimal Power Management"

4. Create a new power profile that is a copy of Minimal Power Management with the name "Minimal CPU Lowest":

> powercfg /c "Minimal CPU Lowest"

NOTE: If you specify a new name that is too long, powercfg /c will fail silently without creating the new power profile.

5. Ensure that Minimal CPU Lowest was actually created:

> powercfg /l

6. Change the CPU throttling parameters in Minimal CPU Lowest:

> powercfg /x "Minimal CPU Lowest" /processor-throttle-ac constant
> powercfg /x "Minimal CPU Lowest" /processor-throttle-dc constant

That's it!

Using Your New Windows Power Profile

Whenever you want to lock the CPU to lowest performance, log in to an account with administrative privileges, go to Control Panel-->Power Options, and select your new "Minimal CPU Lowest" power scheme.

Additional Information

For more info on powercfg see this MS KB article:

How to use Powercfg.exe in Windows Server 2003

What if Lowest Performance is not Adequate?

For experts only

To lock the CPU at a low performance level other than lowest performance (without using BIOS Setup) you will have to use RMClock.
Be forewarned:

- With RMCLock it is possible to misconfigure the CPU freq and voltage so that as soon as RMClock starts running the CPU crashes.

- RMClock requires administrative privileges at runtime. Many people, myself included, consider it unsafe in Windows to use an account with administrative privileges for routine operations (e.g., web browsing, reading HTML email).
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