SenseMi Stage 2: Precision Boost
For almost a decade now, most commercial PC processors have invoked some form of boost technology to enable processors to use less power when idle and fully take advantage of the power budget when only a few elements of the core design is needed. We see processors that sit at 2.2 GHz that boost to 2.7 GHz when only one thread is needed, for example, because the whole chip still remains under the power limit. AMD is implementing Precision Boost for Ryzen, increasing the DVFS curve to better performance due to Pure Power, but also offering frequency jumps in 25 MHz steps which is new.
Precision Boost relies on the same Infinity Control Fabric that Pure Power does, but allows for adjustments of core frequency based on performance requirements and suitability/power given the rest of the core. The fact that it offers 25 MHz steps is surprising, however.
Current turbo control systems, on both AMD and Intel, are invoked by adjusting the CPU frequency multiplier. With the 100 MHz base clock on all modern CPUs, one step in frequency multiplier gives 100 MHz jump for the turbo modes, and any multiple of the multiplier can be used on the basis of whole numbers only.
With AMD moving to 25 MHz jumps in their turbo, this means either:
The base frequency has reduced down to 25 MHz and AMD is able to implement a 136x multiplier to reach 3.4 GHz, or
AMD can implement fractional multipliers, similar to how processors in the early 2000s were able to negotiate 0.5x multiplier jumps, or
Precision Boost only applies to internal clocks that the user doesn’t see or control, but can assist with performance.
Without additional information, the second point in that list seems more in line with what would be possible. If we consider that Zen’s original chief designer was Jim Keller (and his team), known for a number of older generation of AMD processors, a similar technology might be in play here. If/when we get more information on it, we will let you know.
