SpeedStep

The Intel SpeedStep Technology ( EIST or SpeedStep short for " Enhanced Intel SpeedStep Technology" ) is an energy saving function in notebook and desktop processors by Intel.

Generally

SpeedStep was designed to extend the battery life of notebooks (more generally, to reduce the energy requirements of the CPU). With the help of SpeedStep changes the processor 's clock rate, ie, the processing power, depending on the setting and needs. SpeedStep 1.1 detects whether the notebook depends on the outlet or just the battery. For network operation of the processor is clocked at full rated power, and the maximum computing power is available. If the notebook is running on battery power, the clock frequency is reduced, reducing power consumption. At a reduced frequency can also reduce the voltage. Since the energy turnover is the square of the core voltage of the chip, the voltage reduction has the biggest impact on fuel consumption. The lower energy consumption extends the battery life.

From SpeedStep 2.1, the CPU, the so-called " Dynamic Switching " has, in this case the CPU usage is detected and accordingly adjusted the clock rate. The CPU is idle, it automatically overclocked with the lowest clock. However, if the CPU required, such as a compute-intensive application, the CPU clock speed changes up within milliseconds and provides the full power. With special programs such as Speed ​​Switch XP, Notebook Hardware Control or RMClock exact rules can be used to set how SpeedStep has to behave, such as Dynamic Switching on AC power and "fixer minimal CPU clock " on battery power.

Basically, it has in a notebook, which is dynamic switching capability, hardly makes sense to fix the clock rate in network operation at full load, as the unnecessarily high computing power also affects the generated waste heat and therefore operated the fan unnecessarily faster and louder must be. But not only the processor is a major consumer, other components such as the backlight of the screen, hard drive, controller and dedicated graphics cards must be optimized for low power consumption.

In mobile processors

In notebook SpeedStep also influences other components and regulates for example the screen brightness. The software knows the intermediate steps in the clock rates and multiple profiles to either extend the term or to provide more computing power. With the introduction of the Pentium M and the partially switched off cache has been introduced, which further reduces energy consumption.

Use is SpeedStep in different versions in:

• Mobile Pentium III ( Coppermine and Tualatin )
• Mobile Pentium 4
• Pentium M
• XScale processors based on ARM architecture for "embedded devices"
• Processors that build on the basic core (eg Core 2 Duo)
• Intel Atom

The Mobile Celeron and his successor Celeron M have no SpeedStep.

In desktop and server processors

Due to higher clock frequencies and greater chip complexity and associated heat and cooling problems, Intel introduced in many standard processors energy-saving measures.

First (from E0 Stepping) was integrated at Pentium-4/Xeon-Prozessoren an extended stop command, the "Enhanced Halt State " ( C1E ): During an operating system in a phase in which no pending work ( idle state ) through the normal stop command can only turn off the computational units of the CPU, it can additionally reduce the clock on C1E during operation and reduce the tension. However, the energy saving is moderate, since the reduction of the clock and the core voltage is relatively low, and furthermore are only two levels: the idle state or full load.

Since the Pentium 4 600 series (N0 Stepping) is SpeedStep but found in virtually all Intel desktop processors of the middle and upper market segment.

Versions

There are different versions of the Intel SpeedStep technology, which is used in different processors:

Problems

Unlike regular PC games and applications that can emulators that need to emulate exactly different CPU systems become unstable EIST. In this case, only the disabling EIST in the BIOS or the short-term activation of the turbo mode provided that the emulator offers this feature helps.

Even when overclocking EIST can lead to problems.

An unpleasant problem for people with good listening skills is the CPU Whining, which occurs when the CPU is running clocked down and produces vibrations or high notes in the computer.