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.

CCD Clock Speed Mismatch

In pure stock settings, we noticed that the boosting behavior of among the two CCDs is vastly different, with cores on the second CCD boosting anywhere between 100 to 250 MHz lower than their counterparts from the first CCD. This isn't a case of power budget running out and the processor spreading its boost budget lower on the second CCD, as our testing shows, where we applied a lightly-parallelized workload to specific cores in both CCDs, and noticed that even well within the power/thermal limits, the second CCD simply isn't boosting as high as the first one, including the cores AMD marked as "preferred cores" in that CCD. We've reproduced this CCD boosting disparity on even our 7900X sample. Older-gen 5000-series chips such as the 5950X don't exhibit this.


200 MHz difference at 1T


250 MHz at 2T


250 MHz at 3T


100 MHz at all threads active


Comparing the best core on CCD2 to a random core on CCD1 still reveals a big clock difference.

I reached out to AMD and haven't received a response yet. Once I do, I'll update this review.

Overclocking

The Ryzen 9 7950X comes with a fully unlocked multiplier, which makes multiplier-based all-core overclocking very easy. I dialed the voltage up to 1.275 V, which is about the maximum I could run Prime95 at and not overheat by crossing 115°C—even with a powerful AIO. Using Arctic's AIO with "Ryzen offset mounting" helped shave a few degrees off the CPU temperature. At this voltage, with Prime95 running, I kept increasing the multiplier in Ryzen Master until the system became unstable. There was no way that 5.2 GHz all-core would be fully stable, so I settled for 5.1 GHz. You might see some higher overclocks in other reviews, unless these had really good silicon, and/or were paired with exceptional custom watercooling or dry ice/LN2, there's no way these were verified to be stable with Prime95 and only lighter tests were run. Just to clarify, the limit here is not the OC ability/voltage, but the CPU temperature, which limits the voltage you can use.