The reported CPU speed in the Start > Control Panel > System Properties dialogue box depends on a "snapshot" of the speed the CPU is running at the time the system requests it. Newer mobile processors, such as the Mobile Pentium III, Mobile Pentium III-M, and Mobile Pentium 4-M support processor-throttling technology. The processor's frequency and possibly the system bus frequency may be reduced or "throttled down" to conserve battery life. The speed can differ depending on many different factors, such as the power scheme selected, the type and number of programs running, and whether the unit is running on AC or battery power.

Unlike previous versions of Windows, XP has native support for processor performance control. The operating system has built-in support for Intel SpeedStep and AMD PowerNow! Thus, the applets previously required for use with Windows ME, 98, et cetera are no longer necessary.

Processor-throttling technology is dandy, but how do I disable it?

Navigate to Start > Control Panel > Power Options and set the power scheme to Home/Office Desk or Always On.

Home/Office Desk > None (AC) > Adaptive (Battery)
Portable/Laptop > Adaptive (AC) > Adaptive (Battery)
Presentation > Adaptive (AC) > Degrade (Battery)
Always On > None (AC) > None (Battery)
Minimal Power Management (AC) > Adaptive > Adaptive (Battery)
Max Battery > Adaptive (AC) > Degrade (Battery)

Adaptive = Performance state chosen based on CPU demand
Degrade = Starts at lowest performance state, then uses linear performance reduction (stop clock throttling) as battery discharges
None = Always runs at highest performance state

For more information, see:reference

Can I permanently disable this in the registry?

Open your registry, create a new DWORD value, or search and modify the existing value, called "HackFlags." Edit the value according to the settings below.

0 = disable native XP support
1 = use settings inherited from Intel software during XP upgrade
5 = give XP complete support and control over the processor speed; system can support all modes when running on battery

Why does the System Properties dialog box display the CPU speed as 849MHz or 848MHz even though I have an 850MHz CPU and power management is disabled?

According to Microsoft, "because of minor variations in clock frequencies for the CPU and system bus, the current speed may differ from the maximum speed."

Microsoft addresses this issue in the following Knowledge Base articles:

Q311051 - Q303602

Where can I download the SpeedStep Applet for Windows XP/ME/9x/NT/2000?

Intel does not provide the software for download from their site. Check with your notebook PC vendor for the applet. An applet for Windows XP does not exist since the drivers have been included with the operating system.

How can I determine the maximum frequency my Intel mobile processor is capable of running at?

Download the Intel Processor Frequency ID Utility. For mobile processors, the utility should run a special test to determine the maximum frequency the processor is capable of running at.

reference

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by BA edited by Cariad
last modified: 2003-02-18 09:46:18