Intel Speed Select Technology or SST It is a new technology from Intel included in the microprocessors based on the Cascade Lake microarchitecture. This technology allows more exhaustive control of CPU performance and improves consumption in some cases. Each server uses different workloads and has different needs, so the SST family of functions allows for better optimization.
With SST you can configure the CPU to adapt to different workloads, control the base frequency for certain workloads when you need it, etc. Well, all this will be supported on Linux since Linux kernel 5.3, which will be where it is included for the first time. Currently 5.2 is ready, but it will not take long for the first RC of 5.3 to arrive where you can have an idea of what this new version will be and where you can test this new controller.
All machines o servers with Cascade Lake chips with SST support they will be able to get the most out of Linux 5.3. The new driver for SST will allow granular power and performance control, adding configuration profiles that you can adjust from the operating system to dynamically introduce them in real time, and for each core included in the chip.
SST is really in the Xeon processors, so for the home user you will not be able to count on it unless you have a workstation, a Mac, or a server with this type of chip.
These details about Intel SST information on Linux have been known by a series of patches which have been introduced recently to be merged with the main tree of the Linux kernel with a view to being integrated in 5.3. If you want more information, you can read this source, specifically an email, where it is discussed in the LKML. It belongs to the user Srinivas Pandruvada, one of the Intel Corp. workers in Oregon, and dedicated to contributing code to the kernel.
And I'm here waiting for news from Risc-V.