Microsoft's long-anticipated OS Windows 11 launched earlier this month to much trepidation amongst the wider PC enthusiast community. New versions of Windows are generally treated with a degree of justified wariness even if they do offer considerable improvements over the most commonly installed OS, and it can hardly be said that Windows 11 was a game changer in that regard.
So it came as little surprise that the newest Windows was released with a pretty major bug that heavily impacted CPU performance, even if it was in a narrow family of processors. It turns out that the release revision shipped with an issue, potentially involving the new scheduler, that took a hammer to L3 Cache latency and bandwidth of AMD Ryzen 3000 and 5000-series CPUs with a dual CCD design (i.e. those with more than 8 cores).
Synthetic results in AIDA64 were awful, but thankfully the real-world performance penalty appeared to be only terrible and not catastrophic. Perhaps as much as a 5% hit in some instances, more in outlier cases including a minority of games.
Thankfully, earlier today AMD and Microsoft both finally issued fixes that dealt with their particular responsibilities for this problem. Comprised of both a minor Windows update (KB5006746) and revised AMD chipset driver (v3.10.08.506), taken together they have been shown to vastly improve key metrics that were symptoms of the underlying issues.
The updates are a full resolution to the problems as far as AMD are concerned. Microsoft on the other hand will likely iterate on their scheduler throughout the OS's life cycle, particularly as novel architectures are released.
SOURCE: AMD Knowledge Base PA-400