Windows 11 issues with AMD: more performance lost with Update KB5006674, fix with Update KB5006746

[German]Owners of AMD hardware that rely on Windows 11 currently have a difficult time. Already when the operating system was released, there was a warning that there would be performance losses on AMD CPUs. With the cumulative update KB5006674 from October 12, 2021, there was then a further deterioration. However, updates with fixes should come next week – currently Microsoft is already testing the update KB5006746 with insiders.

Performance issues with AMD CPUs

Processor manufacturer AMD had already recently released PA-400, which contains information about known performance issues that have been reported under Windows® 11 when running with compatible AMD processors with certain applications.

• The AMD CPUs can cause extreme outliers in terms of performance degradation in eSports games, ranging from 10 to 15 percent.
• For applications, AMD says the performance degradation is in the 3 to 5 percent range, as noted.

This affects processors supported by Windows 11: all Ryzen CPUs, all Zen+, Zen 2 and Zen 3 CPUs, also the Ryzen 2000, Ryzen 3000, Ryzen 4000 and Ryzen 5000 processors. I had reported in the blog post AMD warns: CPUs run up to 15% slower with Windows 11. However, AMD and Microsoft want to fix these performance losses with updates in October.

Update KB5006674 increase performance issues

On October 12, 2021 (Patchday), Microsoft released the cumulative update KB5006674 for Windows 11 (see Patchday: Windows 11 Updates (October 12, 2021)). This update caused owners of AMD Ryzen processors to experience even higher Level 3 cache latencies than before. The performance, especially in games, drops further. German site heise has covered the topic in detail – and with measurements – in this article. There is another discussion on reddit.com.

Patches for AMD L3 problem coming

There were already first hints from AMD about upcoming patches to fix the problems, but still without dates. At German magazine heise you can read about a planned Windows 11 update for next Tuesday, October 19, 2021. This update KB5006746 is currently already being tested with Windows 11 Insiders in the Beta and Release Preview Channel (see this announcement in the Windows blog). The change log says that an L3 caching problem has been fixed. According to heise, a new chipset driver from AMD should follow on October 21, 2021. This should hopefully solve the problems with the performance losses of AMD CPUs in Windows 11.

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