If you're planning to upgrade to Windows 11, or have done so already, you may want to hold off, as popular AMD Ryzen CPUs are suffering from huge performance hits as high as 15% in single-core workloads, leading to degraded gaming performance.
The issues, which has been noted by various Insiders during testing but only this week acknowledged by AMD and Microsoft, cause performance problems in certain situations, thanks to latency in the L3 cache and the incorrect assignment of CPU cores when running single-core workloads.
The L3 cache performance affects any application that relies on memory or cache latency, with video games being a primary example. Similarly, any games that are single-threaded, for example, may not use the CPU's "preferred core" (the fastest core on the processor) due to a bug that causes them to be assigned to other, less performant cores. This is causing issues especially on the higher core-count CPUs such as the 3900x and 5900x.
The good news is that patches are coming to fix the issues, with both a Windows 11 update and an AMD driver update required. These should be released by the end of October but in the meantime, you may see degraded performance. Sadly, it's also a rather clunky manual workaround to fix at least one-half of the issues.
Similarly, the issues also affect EPYC CPUs, but so far, there's no word of Intel having any issues. We'll be sure to keep an eye on the situation and report any further updates as we learn them.