Clock Frequencies

The following chart shows how well the processor sustains its clock frequency and which boost clock speeds are achieved at various thread counts. This test uses a custom-coded application that mimics real-life performance—it is not a stress test like Prime95. Modern processors change their clocking behavior depending on the type of load, which is why we provide three plots with classic floating point math, SSE SIMD code, and modern AVX vector instructions. Each of the three test runs calculates the same result using the same algorithm, just with a different CPU instruction set.



The weird sawtooth pattern in the chart above is due to the processor clocking down a core when it's not fully loaded. Each core has support for two threads, so when only one thread is running on a core, the CPU thinks it has some free time to save power, which lowers the actual average frequency. When two threads are running on the same core, it will run at its max frequency.

Overclocking

While overclocking the Ryzen 5800X3D wasn't possible, the new 7000 Series X3D CPUs can be overclocked through Precision Boost Overdrive (PBO) and Curve Optimizer (CO). Multiplier-based overclocking is still not available.

First of all, enable PBO and switch to the "manual" mode, which gives you most control. Set the various power limits to something like 200, you can raise them later if you max out one of them. Now the most important part, you must enable Curve Optimizer or you will not see any meaningful gains. Start with a value of -15 on all cores, boot into Windows, and use Ryzen Master to check that everything is setup correctly.

Now run stability tests and games to see if your system is stable. Your temperatures will also be higher, because the CPU will boost higher for longer. With my Noctua NH-U14S I'll hit the 89°C thermal limit pretty quickly, so lowering the Curve Optimizer value is required. Since the 3DV-Cache die is more sensitive to thermals, AMD has decided to lower the temperature limit from 95°C (non 3D VCache Zen 4 CPUs) to 89°C (X3D Zen 4 CPUs). Together with the thick heatspreader, it is very difficult to keep the CPU temperature down, even though your heatsink itself is barely warm.

I managed to shave around 1°C off the temperature by lowering the SOC voltage setting, which saves roughly 10 W heat output from the SOC (memory controller etc). These 10 W get consumed by the CPU cores automatically, the processor will boost slightly higher, until it reaches the temperature limit, you get a bit of extra performance.

Using our Arctic Liquid Freezer II AIO helped a little bit with temperature, but the problem is really not getting rid of the heat at the bottom of the heatsink, but getting the heat from the tiny surface area compute die to move through the IHS. In this regard, the 7800X3D is more difficult to cool than the 7900X3D or 7950X3D, which spread their heat output over two CCDs, i.e. a twice as big surface area.

The 7800X3D is artificially capped to a maximum frequency of 5050 MHz on each core, probably to protect the higher-end X3D CPUs, which are allowed to boost higher. For example, the 7950X3D will boost up to 5250 MHz easily with light loads on it's 3D VCache chiplet.