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| '''SpeedStep''' is a [[trademark]] for a series of [[dynamic frequency scaling]] technologies (codenamed '''Geyserville'''<ref>{{Citation |title=Intel EIST SpeedStep |author=Michael Larabel |authorlink=Michael Larabel |date=February 16, 2006 |publisher=[[Phoronix|Phoronix Media]] |url=http://www.phoronix.com/scan.php?page=article&item=397&num=1 |accessdate=2010-08-09}}</ref> and including SpeedStep, SpeedStep II, and SpeedStep III) built into some [[Intel]] [[microprocessor]]s that allow the [[clock speed]] of the processor to be dynamically changed (to different ''P-states'') by software. This allows the processor to meet the instantaneous performance needs of the operation being performed, while minimizing power draw and heat generation. ''Enhanced Intel SpeedStep'' is sometimes abbreviated as ''EIST''.
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| ==Explanation==
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| Running a processor at high clock speeds allows for better performance. However, when the same processor is run at a lower frequency (speed), it generates less heat and consumes less power. In many cases, the [[CPU core voltage|core voltage]] can also be reduced, further reducing power consumption and heat generation. This can conserve battery power in notebooks, reduce running costs and environmental footprint, extend processor life, and reduce noise generated by variable-speed fans. 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 the processor burden changes.
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| The power consumed by a CPU with a [[capacitance]] ''C'', running at frequency ''f'' and voltage ''V'' is approximately<ref>{{Citation |title=Enhanced Intel SpeedStep Technology for the Intel Pentium M Processor - White Paper |publisher=[[Intel Corporation]] |date=March 2004 |url=ftp://download.intel.com/design/network/papers/30117401.pdf}}</ref>
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| :<math>P = C V^2 f.</math>
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| For a given processor, ''C'' is a fixed value. However, ''V'' and ''f'' can vary considerably. For example, for a 1.6 GHz [[Pentium M]], the clock frequency can be stepped down in 200 MHz decrements over the range from 1.6 to 0.6 GHz. At the same time, the voltage requirement decreases from 1.484 V to 0.956 V. The result is that the power consumption theoretically goes down by a factor of 6.4. In practice, the effect may be smaller because some CPU instructions use less energy per tick of the CPU clock than others. For example, when an operating system is not busy, it tends to issue [[HLT|halt]] instructions, which suspend operation of parts of the CPU for a time period, so it uses less energy per tick of the CPU clock than when executing productive instructions in its normal state. For a given rate of work, a CPU running at a higher clock rate will execute a greater proportion of HLT instructions. The simple equation which relates power, voltage and frequency above also does not take into account the static power consumption of the CPU. This tends not to change with frequency, but does change with temperature and voltage. Hot electrons, and electrons exposed to a stronger electric field are more likely to migrate across a gate as "gate leakage" current, leading to an increase in static power consumption.
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| Older processors, using older versions of the SpeedStep technology, have fewer increments, such as the [[Pentium 4#Mobile Pentium 4 M|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.
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| SpeedStep technology is partly responsible for the reduced power consumption of Intel’s Pentium M processor, part of the [[Centrino]] brand.
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| ==Problems when using SpeedStep==
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| Microsoft has reported that there may be problems previewing video files when SpeedStep (or the AMD equivalent [[PowerNow!]]) is enabled under Windows 2000 or Windows XP.<ref>{{Citation |title=PRB: Poor Performance When You Preview Video |publisher=[[Microsoft]] |url=http://support.microsoft.com/kb/318682/EN-US/}}</ref> It also may decrease reliability when [[overclocking]]{{Citation needed|date=January 2012}}
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| .
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| ==Operating system support==
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| === BSD ===
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| The BSD kernels have full SpeedStep support integration.
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| === Linux ===
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| Operating systems and/or distributions, utilizing [[Linux]] kernel, have full SpeedStep support integrated since kernel version 2.6.
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| === Mac ===
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| [[Mac OS X]] also has SpeedStep built into the kernel, since the release of the Intel version of Mac OS X 10.4 and is already enabled. It cannot be controlled in the System Preference "Energy Saver." To disable this feature, and set a specific clock speed (full speed or reduced) requires a third party application, such as [http://www.coolbook.se/ coolbook].
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| === Solaris ===
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| [[Solaris (operating system)|Solaris]] has supported SpeedStep since [[OpenSolaris]] SXDE 9/07.<ref>{{Citation |title=Introducing Enhanced Intel SpeedStep to Solaris |publisher=[[Sun Microsystems]] |url=https://blogs.oracle.com/mhaywood/entry/introducing_speedstep_on_solaris |accessdate=2008-03-24}}</ref>
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| === Windows ===
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| Older versions of Microsoft Windows, [[Windows 2000]] and earlier, need a special driver and dashboard application to access the SpeedStep feature. Intel's website specifically states that such drivers ''must'' come from the computer manufacturer; there are no generic drivers supplied by Intel which will enable SpeedStep for older Windows versions if one cannot obtain a manufacturer's driver.<ref>{{Citation |title=Processors - Update the Driver for Intel(R) SpeedStep(TM) Technology |publisher=[[Intel Corporation]] |date=2007-01-17 |url=http://www.intel.com/support/processors/sb/cs-003772.htm |accessdate=2007-04-30}}</ref><ref>{{Citation |title=Mobile Intel Pentium 4 Processors - M - Enhanced Intel SpeedStep(R) Technology |publisher=[[Intel Corporation]] |date=2006-07-06 |url=http://www.intel.com/support/processors/mobile/pentium4/sb/CS-007499.htm |accessdate=2007-04-30}}</ref>
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| Under Microsoft [[Windows XP]], SpeedStep support is built into the power management console under the control panel. In Windows XP a user can regulate processor speed indirectly by changing power schemes. The "Home/Office Desk" setting disables SpeedStep, the "Portable/Laptop" power scheme enables SpeedStep, and the "Max Battery" uses SpeedStep to slow the processor to minimal power levels as the battery weakens.<ref>{{Citation |title=Intel SpeedStep, Windows XP, and confusing Power Profiles |author=Michael Chu |url=http://www.orthogonalthought.com/blog/index.php/2007/09/intel-speedstep-windows-xp-and-confusing-power-profiles/ |accessdate=2009-03-10}}</ref> The SpeedStep settings for power schemes, either built-in or custom, cannot be modified from the control panel's GUI, but can be modified using the POWERCFG.EXE command-line utility.<ref>{{Citation |title=Powercfg Command-Line Options |publisher=[[Microsoft]] |url=http://technet.microsoft.com/en-us/library/cc748940.aspx |accessdate=2009-06-11}}</ref>
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| In contrast, AMD continues to supply and support drivers for its competing [[PowerNow!]] technology that will work on Windows 2000, ME, 98, and NT.<ref>{{Citation |title=AMD Turion 64 X2 Dual-Core Mobile Technology Utilities & Updates |publisher=[[Advanced Micro Devices]] |url=http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_871_14098,00.html |accessdate=2007-04-30}}</ref><ref>{{Citation |title=AMD Turion 64 Mobile Technology Utilities & Updates |publisher=[[Advanced Micro Devices]] |url=http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_1202_1073%5E871%5E13349,00.html |accessdate=2007-04-30}}</ref>
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| ==Versions==
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| '''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.{{Citation needed|date=June 2013}}
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| '''V2.1''' (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.
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| '''V2.2''' is 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.
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| '''V3.1''' (EIST) is used with the first and second generation of Pentium M processors (Banias and Dothan cores, 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 (for Banias core) or 133 MHz (for Dothan core). With this technology, Intel also introduces realtime Level 2 cache capacity variation, further improving power savings.
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| '''V3.2''' (Enhanced EIST) is adapted for multi-core processors with unified Level 2 cache.
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| ==See also==
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| * [[Advanced Configuration and Power Interface|ACPI]]
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| * [[AMD]]'s [[Cool'n'Quiet]] and [[PowerNow!]]
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| * [[Power management]]
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| * [[Intel Turbo Boost]]
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| * [[CPU-Z]] is an application for Windows that displays core speed and [[Voltage Identification Digital|VID]] in real-time which may be helpful in determining whether SpeedStep is functioning correctly
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| ==Notes==
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| {{Reflist|30em}}
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| ==External links==
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| * [http://www.bay-wolf.com/speedstep.htm SpeedStep FAQ]
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| {{Intel technology}}
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| {{CPU power saving technologies}}
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| [[Category:Intel products]]
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| [[Category:Computer hardware tuning]]
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| [[Category:Clock signal]]
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Hello and welcome. My title is Irwin and I completely dig that name. She is a librarian but she's always needed her personal business. Years ago we moved to North Dakota. Doing ceramics is what my family and I enjoy.
my page :: http://L.keroup.com/