Incorrect CPU frequency is displayed in the DCUI for Intel Speed Select Technology Power Profile (SST-PP)

Products

• VMware vSphere ESXi

Issue/Introduction

The CPU speed shown in the DCUI may not match the guaranteed base frequency of the current Intel Speed Select Technology Power Profile (SST-PP).

Cause

Intel CPUs with the feature SST-PP (Speed Select Technology Power Profiles) can be set to several power profiles.  Using a different power profile allows you to have an increased guaranteed base frequency (P1 frequency) in return for having fewer active cores.

The ESXi DCUI identifies the system's CPU by showing its CPUID brand string, which in some cases includes the CPU's speed.  On Intel Speed Select processors, the brand string does not change to reflect the current SST-PP profile.  Instead it will display the guaranteed base frequency of the profile in which all cores are active.

Resolution

vSphere ESXi does not support displaying the current SST-PP P1 frequency in the DCUI.

vSphere ESXi does not support Intel SST in general. In most SST use cases, SST creates a CPU socket to have a "Non-Uniform" array of Cores with different frequencies of operation. vSphere ESXi does not perform any dynamic placement of VMs based on SST. Customers may observe that VMs may be slightly less performant when landed on a lower frequency core.