It’s probably fair to say that Windows 11 and AMD Ryzen processors haven’t had the best time as of late of. As soon as the original 21H2 version released last year to the public, issues related to the CPPC2 were discovered. These were later fixed with a chipset driver update.
Now with the recent Windows 11 version 22H2 release, it looks like a new problem is bugging the Zen 4-based Ryzen 7000 series CPUs. CapFrameX (CFX) has discovered that when a single CCD (CPU Compute Die) on the 16 core Ryzen 9 7950X is active, the configuration is able to outperform the default dual CCD 7950X. Each Zen 4 CCD features eight cores along with its cache, among other things Hence essentially, an octa-core Zen 4 CPU is able to beat out the higher core count 16 core variant.
To better understand the issue and assess the scenarios affecting the problem, CFX decided to test two other instances where simultaneous multi-threading (SMT) was disabled. Hence in a single CCD situation with SMT disabled, the 16 core 32 thread 7950X was now reduced to an eight core CPU with eight threads.
Just like the single CCD case, the SMT-off situation also yielded similar results that are showing better performance with fewer threads.
This does not seem like a one off case either as seasoned hardware benchmarker Hardware Unboxed (HBU) noticed similar problem on their RTX 4090 test system. And apparently, it has been happening much more frequently in recent times.
Something interesting I’ve noticed as I updated all our CPU data with the RTX 4090 is that there are now many instances where single CCD Ryzen CPUs are faster (better for driving high fps). Previously the R5 3600X never really beat the R9 3950X for example, where as now it does.
— Hardware Unboxed (@HardwareUnboxed) October 15, 2022
The performance issue seems to be prevalent on Windows 11 22H2 (via @OneRaichu), and from the looks of it, it seems like Windows 11 22H2 is having a scheduler issue on the new Ryzen 7000 CPUs which is why more threads aren’t helping. There could also be a driver bug at play here similar to the Nvidia fiasco that happened recently. Perhaps the GPU driver itself is not properly utilizing the extra threads.