ASUS Dynamic OC Switcher allows dynamic switching between AMD Precision Boost Overdrive and OC mode on AMD Ryzen processors. It is was first available exclusively on the ASUS ROG Crosshair VIII Dark Hero and now also made it to the ASUS ROG Crosshair VIII Extreme.
AMD Ryzen CPUs have two overclocking modes: PBO and OC Mode.
Precision Boost Overdrive and Precision Boost Overdrive 2 allows the user to change a limited number of parameters that are included in the PBO algorithm. However, it is still the AMD PBO proprietary algorithm that will eventually determine the performance of the system.
OC Mode disables all the limiters, voltage controllers, and most protections. OC Mode is automatically activated when the user raises the base frequency. A major downside of OC Mode is that all automatic overclocking features are disabled too. That means you lose the benefit of the high single-threaded frequencies that PBO offers.
Dynamic OC Switcher is ASUS’ very clever way of solving one of AMD’s biggest problems when overclocking: while Precision Boost Overdrive provides the best benchmark performance in single and low-threaded benchmark applications, the best multi-threaded performance is achieved by manually overclocking. So, you have to compromise: best single threaded performance or best multi-threaded performance.
Dynamic OC Switcher gives us the best of both worlds as it allows the system to actively switch between Precision Boost Overdrive and manual OC mode. As I have demonstrated in previous SkatterBencher videos, DOS requires little additional configuration work. Think about DOS as follows: it is exactly like Precision Boost Overdrive, but the lowest frequency is manually set by us. So, we need to know two things:
- What is the lowest frequency we will allow
- At which point do we want DOS to switch between PBO and OC Mode
Sadly, we cannot simply configure a minimum frequency and have the system switch based on that. Instead, we need to use a proxy metric: a certain current threshold or a certain temperature threshold. There is not one specific method of determining the right threshold, so I’ll show you two examples: one with Prime95 Small FFTs and one with Cinebench R23.
Configuration with Prime95 Small FFTs
The exact trigger point will depend on your CPU, your motherboard, your cooling, and your system. One way of identifying the right trigger point is to check the CPU current during a benchmark workload. I’ll give you an example.
First, make sure the system is set to default settings with Precision Boost Overdrive enabled. Then go in the Operating System, you can use HWinfo and Prime 95 without AVX. Gradually increase the amount of Prime 95 threads until you see the operating frequency drop below your desired manual overclock. When this happens, check the CPU current in HWinfo. This is the value you can use to configure DOS OC.
As a rule of thumb, you should expect a high manual overclock to have a low current threshold and vice versa.
Configuration with Cinebench R23
For our minimum frequency, we choose our maximum stable manual overclock. I verified the maximum stable manual overclock of this CPU using Prime 95 Small FFTs with AVX disabled and ended up with a ratio of 46.25 for CCD0 and 45.50 for CCD1 with a core voltage of 1.345V. So, our minimum frequency will be the average of 4625 and 4550 MHz, so 4587 MHz.
In the Operating System, we first open HWiNFO. We make sure we can monitor both the Effective Clock Frequency and the CPU Core Current.
Then we start the Cinebench R23 multi-threaded benchmark workload and change the affinity to 1 core in task manager. Now monitor the effective clock frequency. It will be higher than our target of 4587 MHz. Now you can gradually increase the Cinebench R23 thread count.
When you reach 4587 MHz or below, check the CPU Core Current reading. This value will be our input for the DOS Current Threshold.
As you can see, I’m not enabling threads sequentially. That’s because as some cores are better than others, they will boost to higher frequencies. So, I want to make sure I am not too conservative when picking the switching point.
I checked which cores are the best by running the CoreCycler application and checking the peak effective clock using HWiNFO.
In our case, we reach the frequency of 4587 MHz at 7 active threads. The current varies between 43.7 and 51.5 amps. To be on the safe side we pick 47A as the Current Threshold.
So, to reiterate what’s happening: Dynamic OC Switcher will switch between OC mode and Precision Boost Overdrive when the CPU current hits 47A. Anything above 47A will engage manual OC mode; anything below 47A will engage Precision Boost Overdrive.
ASUS Dynamic OC Switcher in SkatterBencher Guides
We use ASUS Dynamic OC Switcher in the following SkatterBencher guides: