Intel Turbo Boost and AMD Turbo CORE technologies are features that allow processors to achieve additional performance when it is most useful (that is, at high system loads). However, this feature increases CPU core energy consumption, so Windows Server 2012 configures Turbo technologies based on the power policy that is in use and the specific processor implementation.
Turbo is enabled for High Performance power plans on all Intel and AMD processors and it is disabled for Power Saver power plans. For Balanced power plans on systems that rely on traditional P-state-based frequency management, Turbo is enabled by default only if the platform supports the EPB register.
Note At the time of writing this guide, the EPB register is only supported in Intel Westmere and later processors.
For Intel Nehalem and AMD processors, Turbo is disabled by default on P-state-based platforms. However, if a system supports Collaborative Processor Performance Control (CPPC), which is a new alternative mode of performance communication between the operating system and the hardware (defined in ACPI 5.0), Turbo may be engaged if the Windows operating system dynamically requests the hardware to deliver the highest possible performance levels.
To enable or disable the Turbo Boost feature, you must configure the Processor Performance Boost Mode parameter. Processor Performance Boost Mode has five allowable values, as shown in Table 5. For P-state-based control, the choices are Disabled, Enabled (Turbo is available to the hardware whenever nominal performance is requested), and Efficient (Turbo is available only if the EPB register is implemented). For CPPC-based control, the choices are Disabled, Efficient Enabled (Windows specifies the exact amount of Turbo to provide), and Aggressive (Windows asks for “maximum performance” to enable Turbo). In Windows Server 2012, the default value for Boost Mode is 3.
Table 5. Processor Performance Boost Mode parameter values
Value (Name)
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P-state-based Behavior
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CPPC Behavior
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0 (Disabled)
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Disabled
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Disabled
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1 (Enabled)
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Enabled
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Efficient Enabled
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2 (Aggressive)
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Enabled
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Aggressive
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3 (Efficient Enabled)
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Efficient
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Efficient Enabled
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4 (Efficient Aggressive)
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Efficient
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Aggressive
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The following commands set Processor Performance Boost Mode to Enabled on the current power plan (specify the policy by using a GUID alias):
Powercfg -setacvalueindex scheme_current sub_processor PERFBOOSTMODE 1
Powercfg -setactive scheme_current
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