SpeedStep
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SpeedStep™ is a series of technologies (including SpeedStep, SpeedStep II, and SpeedStep III) built into some Intel processors. SpeedStep allows the clock speed of a processor to be dynamically changed by software. 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, allowing 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 4-M 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.
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. Linux has full speed step support already integrated in the kernel and under Microsoft Windows XP, the speed step 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.History
- 1980
- The halt command stops the CPU. Since it is fabricated using CMOS technology, no energy is used for the CPU logic.
- 2003
- Modern mainboards have voltage regulator modules (which are a kind of switch-mode power supplies) integrated into the mainboards them selves, which can often be programmed by the mainboards bios, to accommodate the specific CPU (speedstep-state) and its requirements. Lower voltage means longer clock cycle and less energy per cycle.
- 2005
- The halt command also stops the clock [link]
- 2006
- The halt command stops the voltage regulator modules. When an interrupt restarts the CPU it first has to be "charged" (takes about 2 µs). With only short bursts of CPU activity most of the activity takes place at low voltage.
See also
External links
- [SpeedswitchXP - CPU frequency control for notebooks]
- [RMClock] - similar to SpeedSwitchXP but more complicated to set up, although does support Core Duo processors
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CPU power saving technologies
Intel SpeedStep | AMD Cool'n'Quiet | AMD PowerNow! | Transmeta LongRun | Transmeta LongRun2 | VIA LongHaul (italics indicate technologies for non-x86 processors) |
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