Intel SpeedStep

The Enhanced Intel SpeedStep Technology ™ or EIST represents a series of technologies (including SpeedStep, SpeedStep II and SpeedStep III) implemented in some Processeur S Intel which authorizes a dynamic change of the Fréquence of clock on request for a software.

Principle

To make function the processor at a frequency of very high clock generates better performances. Nevertheless, when it functions at less low frequency, the supply voltage of the heart of CPU can be reduced. This change of tension implies a fall of electricity consumption as well as a reduction in thermal dissipation. The advantages of such a process are numerous:

to improve autonomy of the laptops
to increase the lifespan of the processor
to decrease the nuisances related to a high release of heat
to reduce noise pollutions related to the ventilation system charged to dissipate produced heat

By using SpeedStep technology, the user can choose the best compromise between autonomy and the performance, or even let the system undertake automatically to choose the most effective frequency according to the load at a given moment.

For example, a processor Pentium M conceived to function at a maximum frequency of 1.5GHz can operate at any frequency between 600MHz and 1.5GHz, according to a step of 100MHz (functionalities of SpeedStep III). It should be noted that the older processors, like the Pentium 4-M, will have less intermediate values.

SpeedStep technology is partly responsible for the reduced consumption of the processors Intel Pentium M, which is generally implemented in laptops stamps Centrino.

Support of the operating systems

SpeedStep technology is completely controlled by the operating system, which must be able to deal with the management of the modifications of frequencies to the flight.

Microsoft Windows

On the old operating systems of Microsoft, such as Windows 2000 and older, a specific pilot as well as a control panel are necessary to the use of SpeedStep. The official site of Intel indicates that the pilot must imperatively come from the computer manufacturer, and Intel does not seem to have realized of generic pilot if the manufacturer would not place it at the disposal.

For the more recent systems (Windows XP and later), the support of SpeedStep is dealt with as a native in the control panel. This process is not easier because it requires to change profile of consumption to have an influence on the frequency of operation of the processor.

Third software solutions exist to support more effective SpeedStep of manner, such as for example Notebook Hardware Control, a software of optimization of consumption for laptop which makes it possible to control the frequencies of the processor directly (like their associated tensions).

Linux

Linux has a complete support directly integrated in the core, which thus requires an access Root (administrator) or to install a demon chrooté, whose activation varies largely according to the core (2.4/2.6) and that one can describe as " easily activated and directly skeletal according to the needs for the utilisateur" , since it is enough (for example into 2.4) to seize on the keyboard:

“ cat /proc/acpi/processor/CPU0/performance ” posts the various performance levels

to analyze the resulting table, to pass in root mode by known then to type the password of the administrator, then to type:

“ echo X > /proc/acpi/processor/CPU0/performance ” sends the order to the processor to pass to a performance level

to pass the CPU in Xieme mode of performance and finally to type “ exit ” to leave the administrator mode.

MacOSX

With the arrival of the processors Intel in the laptops Apple MacBook and MacBook Pro, SpeedStep technology is supported today by MacOSX. As for Windows XP, the change of frequency is at the disposal of the system, which will choose the frequency most adapted according to the load and of the selected profile.

There exist also software which makes it possible the user to define in a precise way a given frequency, like Coolbook.

Versions

V1.1

Present in the second generation of processors Pentium III, this version makes it possible the processor to commutate between two modes: high and low frequency. This change is carried out by a change of the multiplying coefficient of the processor. The consumption of such a processor, which borders the 20 Watt S with 1Ghz, can be reduced with 6Watts with 600Mhz.

V2.1

Also called Enhanced SpeedStep , it is present in Pentium III Mobile and is similar to the previous model, but uses a weaker supply voltage for the low frequency than for the high frequency.

V2.2

The adaptation of the Enhanced SpeedStep for Pentium 4-Mobile allows a processor consuming 30Watt normally 1.8GHz to require only 20Watts with 1.2GHz.

V3.1

The second generation of Pentium Mobile (heart Banias, used in the Centrino platforms) is seen equipped with a new version, the EIST , which makes it possible the processor to vary its fréqence from 40% to 100% of its rated frequency, by step of 100MHz. With this version Intel introduces the variation of the level of L2 mask to the flight, to increase the reduction of energy further).

V3.2

Called Enhanced EIST , this version is adapted to the processors Dual Core with Cache L2 unified

See too

AMD Calm Cool' & PowerNow!

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