Intel C2518 FH8065501516710 Data Sheet

Intel

®

 Atom™ Processor C2000 Product Family for Microserver

September 2014

Datasheet, Vol. 2 of 3

Order Number: 330061-002US

167

Intel

®

 Turbo Boost Technology enables higher performance through the availability of 

increased core frequency under certain configurations and workloads. Turbo allows 

processor cores to run faster than the specified operating frequency if the processor is 

operating below rated power, temperature, and current specification limits of the 

system. Turbo is engaged with any number of cores or logical processors enabled and 

active, enabling increased performance of both multi- and single-threaded workloads.

The BIOS enables/disables turbo features. The power-on default value of 

IA32_MISC_ENABLES[38] indicates to the BIOS if the turbo features are present. A 

default value of 1 indicates that turbo features are present and disabled. The BIOS 

clears the IA32_MISC_ENABLES[38] to 0 to enable turbo. A reset-default value of 0 

indicates that turbo features are disabled and not available.

The Operating System (OS) and applications must use CPUID.06H:EAX[1] to detect 

whether the BIOS has enabled turbo features. If IA32_MISC_ENABLES[38] is set, 

CPUID.06H:EAX[1] returns 0.

Because IA32_MISC_ENABLES[38] is defined per-package, CPUID has to read from the 

uncore to get MISC_ENABLES[38]. The OS or BIOS manages read-modify-write 

conflicts cross-core. Setting IA32_MISC_ENABLES[38] on any core causes the SoC to 

disable turbo operation for ALL cores.

Certain software workloads may not be able to tolerate the non-deterministic aspects 

of turbo operation. The software temporarily disables turbo operation by setting 

CLOCK_CR_GEYSIII_CONTROL[32] bit of the IA32_PERF_CTL Model-Specific Register 

(MSR) [MSR 0199h]. As previously mentioned, disabling turbo on any core causes 

turbo to be disabled for ALL cores.

Configuration of certain turbo-power budget settings is accessible by the OS/driver 

software via SoC Sideband (SB) registers. PKG_TURBO_POWER_LIMIT configuration 

registers are duplicated in the SB register space for this purpose. The MSR copies of the 

registers are initialized by the BIOS to typical recommended settings and are 

overridden with more conservative values by the OS/driver by programming the 

corresponding SB registers. The SoC power management reads both copies of the 

registers and applying the more restrictive settings to the turbo algorithms.