Intel Per Core Voltage - SkatterBencher

Intel Per Core Voltage allows you to set a specific target voltage for every individual core inside your CPU.

The feature was first introduced on Skylake-X high-end desktop in 2017 and was most recently implemented on the Sapphire Rapids high-end desktop platform. The feature only came to mainstream desktop in 2021 with Alder Lake. While it may seem like a straightforward feature, the name is slightly misleading.

Configuration

This feature allows the user to assign a different static or adaptive voltage to each CPU core, depending on the platform topology.

On high-end desktop or workstation CPUs which rely on a fully integrated voltage regulator (FIVR) to supply the voltage to the cores, you can set an core specific static or adaptive voltage. However, on mainstream desktop where a single, external VccIA voltage rail supplies all cores with the same voltage, you can only set a core specific adaptive voltage.

In case of the static mode, each core’s static voltage is applied across all scenarios and CPU ratios.
In case of adaptive mode, each core’s adaptive voltage maps to the CPU’s “OC Ratio.” The OC Ratio is the highest configured CPU ratio across all cores (and ring) and settings.

In adaptive voltage mode, each CPU core will have its own unique V/F curve interpolated from the set per core adaptive voltage and the shared OC ratio. You can also combine this feature with the Per Core Ratio Limit feature.

Do remember that when we set a Per Core Ratio Limit, counter-intuitively, this Ratio doesn’t act as a core-specific OC Ratio but limits what parts of the core-specific V/F curve can be used.

In the example below, where 52X is mapped to 1.40V, if we set the Per Core Ratio Limit to 51X, the CPU core will boost up to 5.1 GHz at a voltage interpolated between 52X at 1.40V and 48X at 1.30V.

The Per Core Adaptive Voltage is most useful to give some cores a little extra voltage at the top end of the voltage frequency curve. The Per Core Static Voltage is most useful if you want to set a static ratio for each core and find the lowest stable voltage for a given frequency to maximize power efficiency.