Intel Turbo Boost Technology - How It Affects Processor Speed

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This article describes the Intel Turbo Boost functionality in supported Intel Processors.

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Select Intel processors support a variable clock that is controlled by the Intel Turbo Boost Technology to increase, or decrease the processor clock speed depending on the load placed upon it.

Intel Turbo Boost Technology is activated when the operating system requests the highest performance state of the processor. The processors' performance states are defined by the Advanced Configuration and Power Interface (ACPI) specification.
Maximum turbo frequency indicates the highest possible frequency achievable when conditions allow the processor to enter turbo mode. Intel Turbo Boost Technology frequency varies depending on workload, hardware, software, and overall system configuration.

Availability and frequency upside of Intel Turbo Boost Technology state depends upon a number of factors including, but not limited to, the following:

• Type of workload
• Number of active cores
• Estimated current consumption
• Estimated power consumption
• Processor temperature

When the processor is operating below these limits and the user's workload demands additional performance, the processor frequency will dynamically increase until the upper limit of frequency is reached.

A system that supports Turbo Boost Technology may be marketed with the maximum boosted processor speed listed, but when the system is not requesting maximum performance, or when viewed in the BIOS, the processor speed will be reported as the un-boosted default speed.

The Intel I7-4940, for example, would display the following characteristics in a Precision M6800:


 

1. 3.10 GHz is reported in the BIOS. This is the base frequency of the I7-4940
2. 3.10Ghz is what the BIOS is currently clocking the processor to
3. The maximum frequency the BIOS can clock the processor to is 3.3Ghz
   
    

To save power when in the OS and the system is idling (low processor load), the processor will attempt to clock down to its minimum base clock speed of  800Mhz. The 800Mhz is a theoretical value that cannot always be achieved but it will run at a frequency arbitrarily close to that.


 

1. All cores are idle, no load.
2. The Intel Turbo Boost Monitor reports the values defining the processor as read from the processor.
3. The Intel Turbo Boost Monitor reports that the Turbo Boost mode is inactive.
4. Processor currently running near its base minimum frequency of 800Mhz.

When the system load is increased significantly, the OS will activate Turbo Boost mode and then clock the processor up the max "Turbo" frequency that it can boost the Processor to (provided all conditions allow it). The Intel Turbo Boost Monitor tool can show when Turbo Boost is active and will indicate the max. theoretical speed that can be achieved. Again, this value will not be the actual value that the processor is running at but will be arbitrarily close. BIOS and the OS are not capable of directly showing when this is occurring.

 
 

1. All cores loaded to 100%
2. Turbo Boost mode is now active and the monitor tool is reporting the targeted maximum Turbo Boost frequency that is supported by the CPU as it is currently configured (4Ghz).
3. The actual frequency that the processor cores are currently running at (3.896Ghz). 4GHz is the maximum theoretical limit and the processor may not may not be able to achieve the full value, but it will target the value as closely as possible.

 

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