Clock Frequencies

The following chart shows how well the processor is able to sustain its clock frequency, and what boost clock speeds are achieved at various thread counts. This test uses a custom-coded application that mimics real-life performance (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 the 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.

Overclocking

Just like all other Ryzens, the Ryzen 9 3900XT has its multiplier unlocked, which simplifies overclocking greatly. You just dial in the desired multiplier and are done. Overclocking support is very good on all AMD AM4 motherboards.

Our Ryzen 9 3900XT sample overclocked much better than the Ryzen 9 3900X. The 3900X struggled with 4 GHz, but the 3900XT managed 4.2 GHz, although it took quite a bit of voltage, 1.425 V. This increased cooling requirements, but was still manageable with air cooling. With a 240 mm AIO watercooler, it definitely felt like 4.3 GHz was in reach, but I couldn't get the CPU fully stable with AVX loads.