Amd will resolve the differences between the 'best' and 'preferred' cores

In recent weeks there has been an increase in discussions at AMD about how the new Ryzen 3000 processors interact with Windows, and in particular about how the Best Cores and Preferred Cores functions, where differences arise between what Windows interprets as 'better cores' and what the Ryzen Master tool interprets.

Currently there are discrepancies between the best cores and preferred cores that are managed by Windows and Ryzen Master

Today AMD is officially commenting on the situation and why it arises, while also describing what it is doing to remedy the discrepancies in the data.

Ryzen 3000 are the first AMD products to use an ACPI feature called CPPC2 (Collaborative Power and Performance Control 2) which is an API interface between the chip's firmware (essentially the UEFI BIOS and AGESA) and an operating system like Windows. The interface allows hardware to better communicate its frequency and power management features and settings to the operating system.

What is the matter with this? That the processors communicate another set of data through their own "Ryzen Master" tools and proprietary APIs, which differs from that of Windows, and it is the relationship between these "best cores" and the "preferred cores" of CPPC2 that has caused a bit of confusion since the original release in July.

The discrepancies have been there since the launch of the Ryzen 3000 series. In most situations and configurations, the actual CPU cores that are being loaded into the operating system under single-threaded or light-threaded workloads have never been matched the best CPU cores, as reported by Ryzen Master. This can be seen with any generic monitoring utility such as the task manager.

The discrepancy here lies in the actual mapping between the Ryzen Master "Best Cores" information and the SMU APIs, and the "Preferred Cores" mapping that AMD firmware communicates via CPPC2 to the operating system.

The easiest way to view the configuration settings that CPPC2 communicates to Windows is to view the corresponding Windows “Kernel-Processor-Power” system log entries in the Windows Event Viewer, as shown above in the screenshot of screen.

The “Best Cores” defined by SMU and reported by Ryzen Master are decided based on the electrical properties, and are coded at the time of factory die-cutting. The "preferred cores" defined by CPPC2 are those to which AMD wants the OS developer to send most of the traffic, not only because of their superior physical or electrical properties, but also because they are optimal for the core rotation policy from the Windows programmer. The Windows scheduler is programmed not to indefinitely keep an application work thread assigned to a particular kernel too long, but to rotate it periodically between a pair of two kernels. The rationale for this is thermal management (distributing heat through two spatially separate cores).

AMD promises that it will update this feature to show the preferred cores much more clearly and that there will be no mismatches between the operating system and Ryzen Master. We will keep you informed.

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