Enhanced Intel SpeedStep® Technology On Mobile Frequently Asked Questions for Processors

• Separation of voltage and frequency changes. By stepping voltage up and down in small increments, the processor is able to reduce periods of system unavailability that occur frequency change. The system is then able to transition between voltage and frequency states more often, improving balance between power and performance.
• Clock partitioning and recovery. The bus clock continues running during state transition, even when the core clock and phase-locked loop are stopped, which allows logic to remain active. The core clock is also able to restart far more quickly under Enhanced Intel SpeedStep Technology than under previous architectures.

Enhanced Intel SpeedStep Technology reduces the latency associated with changing the voltage/frequency pair, or P-state. Transitions can be undertaken more frequently, enabling more granular demand-based switching, and the optimization of the power and performance balance based on demand. Enhanced Intel SpeedStep® Technology and Demand-Based Switching on Linux* gives developers an overview of the support for Enhanced Intel SpeedStep Technology, and demand-based switching under Linux*. The article is also a ready reference for developers interested in new user-level or in-kernel policy based on Enhanced Intel SpeedStep Technology.

More resources for Enhanced Intel SpeedStep Technology, processor power, and thermal specifications:

1. If necessary, download and run the latest BIOS update for your motherboard.
2. Enable Enhanced Intel SpeedStep Technology in the BIOS. If the BIOS is from American Megatrends, Inc.*, under the Advanced tab, set to Enabled.
3. Turn Enhanced Intel SpeedStep Technology on in the OS. Currently, for Microsoft Windows XP SP2 operating systems, the default setting is off. To turn it on, do the following:
   1. Click Control Panel > Power Options.
   2. Under the Power Schemes drop down menu, select Minimal Power Management.

To verify that Enhanced Intel SpeedStep Technology is enabled, do the following:

1. Close all applications and ensure that Microsoft Windows* OS is in idle mode.
   1. Press Ctrl Alt Delete and select the Performance tab. Verify that CPU usage is 0%.
2. Right-click My Computer and select Properties.

Under the General tab, look at the installed processor speed. If Enhanced Intel SpeedStep Technology is enabled, two processor speeds are listed. The first speed lists the specified speed of the processor. The second speed is the current operating speed. If both processors list the same speed, repeat steps 1-3, making sure the OS is in idle mode, and CPU usage is 0%.

First, determine if the Enhanced Intel SpeedStep Technology driver is working properly. Use the Intel® Processor Identification Utility. The utility shows the Intel® mobile processor installed, and whether it supports Enhanced Intel SpeedStep Technology. Next, see if the frequency changes. Run the utility while plugged into an AC outlet, then run the utility drawing power from the battery.

When powered by a battery, the processor drops to a lower frequency and voltage, conserving battery life, while maintaining a high level of performance. Manual override lets you boost the frequency back to high frequency, allowing you to customize performance when powered by a battery

Different from the previous versions of Microsoft Windows, the Enhanced Intel SpeedStep® Technology driver is built into Microsoft Windows XP. With the built-in driver, you do not have an icon in the system tray of the taskbar, nor the power applet located in the Control Panel. Without the icon and applet, it can be difficult to determine if Enhanced Intel SpeedStep technology is operating correctly.

Check the following:

• Make sure that your processor and operating system support Enhanced Intel SpeedStep® Technology. See system requirements.
• Make sure Enhanced Intel SpeedStep Technology driver is loaded. The driver is only available from the laptop manufacturer or vendor.

  Note Microsoft Windows* XP automatically includes the drivers.

• Make sure that Enhanced Intel SpeedStep Technology is not disabled in the CMOS setup program (BIOS).
• Check the settings in the Power applet in the Control Panel.
• Check with your system manufacturer to see if they recommend updating the BIOS.