SpeedStep
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SpeedStep™ is a series of technologies (including SpeedStep, SpeedStep II, and SpeedStep III) built into some Intel processors that allows the clock speed of a processor to be dynamically changed by software
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[edit] Explanation
Running the processor at higher clock speeds allows for better performance. However, when the processor is run at a lower speed, its core voltage can be reduced; both of these changes allow for reduced power consumption and heat dissipation. This can conserve battery power in notebooks, extend processor life, and reduce noise from cooling apparatus. By using SpeedStep, users can select the balance of power conservation and performance that best suits them, or even change the clock speed dynamically as processor burden changes.
For example, a Pentium M processor marketed at 1.5 GHz can run at any speed between 600 MHz and 1.5 GHz, at 200 MHz increments, using SpeedStep III.
However, older processors have fewer increments, such as the Pentium 4-M. For example, a 1.7 GHz Pentium 4M can run at 1.6 GHz, at 1.2 GHz, and at 786 MHz.
SpeedStep technology is partly responsible for the reduced power consumption of Intel’s Pentium M processor, part of the Centrino brand.
[edit] Operating system support
Under older Microsoft Windows operating systems, such as Windows 2000 and lower, a special driver and a dashboard application was needed to control the processors. Intel's website specifically states that such driver must come from your computer manufacturer and there appear to be no generic drivers available which will enable SpeedStep for Windows 2000 versions and older if you cannot obtain a manufacturer's driver. There is no such SpeedStep driver available from Intel's website.[1] [2]
In contrast, AMD continues to supply and support drivers for its competing PowerNow! technology that will work on Windows 2000, ME, 98, and NT. [3] [4]
Linux has full SpeedStep support already integrated in the kernel and, under Microsoft Windows XP, SpeedStep support was built into the power management console under the control panel. This actually made it more difficult to regulate the processor's speeds because it could only be done indirectly, by changing the power schemes.
[edit] Versions
V1.1 is used by second generation Pentium III processors. It enables the CPU to switch between two modes: high and low frequency. This is done by modifying the CPU's multiplier. A 1 GHz Pentium III consuming about 20 watts could be reduced to 600 MHz which reduces the power consumption to about 6 watts.
V2.1 aka Enhanced SpeedStep is used in Pentium III-Mobile processors and is similar to the previous version, but in the low frequency mode the CPU also uses a different voltage than the high frequency mode.
V2.2 is Enhanced SpeedStep adapted for Pentium 4-Mobile processors. With this a 1.8 GHz Pentium 4-M consuming about 30 watts can lower its frequency to 1.2 GHz, thus reducing power consumption to about 20 watts.
V3.1 named EIST is used with the second generation of Pentium Mobile processors (Banias core, used in Centrino platforms). With this technology the CPU varies its frequency (and voltage) between about 40% and 100% of its base frequency in increments of 100 MHz. With this technology Intel also introduces realtime Level 2 cache capacity variation, further improving power savings.
V3.2 aka Enhanced EIST is EIST adapted for dual core processors with unified Level 2 cache.
[edit] See also
[edit] External links
[edit] Notes
- ^ SpeedStep drivers must come from manufacturer. See. [1]
- ^ More, SpeedStep drivers must come from manufacturer. See. [2]
- ^ AMD Drivers for Turion 64 X2 including PowerNow!. See [3]
- ^ AMD Drivers for Turion 64 including PowerNow!. See [4]
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CPU power saving technologies
(italics indicate technologies for non-x86 processors) |
