Windows 11: First round of patches further worsens performance with Ryzen CPUs

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All Ryzen processors currently run slower under Windows 11 than when using Windows 10. This is due to two problems that affect Microsoft’s scheduler, among other things: It no longer recognizes the fastest CPU cores and therefore distributes computing tasks suboptimally, and the level- 3 cache way too slow.

The cache problem has worsened since the first major patch round of Windows 11, the so-called Patch Tuesday on October 12th. We tested the Zen 3 combination processor Ryzen 5 5600G under a current Windows 11 installation with AIDA64, in which the L3 cache works with a latency of a good 40 ns. Before the patches, the latency was in the low 30 range. At the same time, the read and write throughput dropped sharply to 96 GB / s at best.

Under Windows 10, the same system has an L3 latency of 12.4 ns and a throughput of up to 378 GB / s. Since 3D games are sensitive to memory latency and throughput, the performance drops particularly sharply there. Before Patch Tuesday, AMD spoke of an average of 10 to 15 percent lower frame rates. The recommendation is still that if you are using a Ryzen processor and using the system primarily for gaming, you should stick with Windows 10.

Ryzen 5 5600G on Windows 11 with high L3 cache latency and low throughput.
(Image: Denis Fröhlich / c’t)

Incidentally, the Ryzen 5 5600G shows that the increased L3 cache latencies are not due to AMD’s CCX design, i.e. the computing cores do not access the intermediate buffer of other core clusters – the tested six-core processor only has a single core complex (CCX) .

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Outgoing from the meanwhile, data is circulatingwhen allegedly patches for the performance problems should appear. Accordingly, Microsoft wants to provide a Windows 11 update with a fix for the L3 cache from October 19, 2021. A new chipset driver from AMD will follow on October 21, 2021, with which Windows 11 will again recognize the fastest CPU cores via the API Collaborative Power and Performance Control 2 (CPPC2).

We asked AMD whether the data was correct and only received the standard statement that AMD and Microsoft are working on the problems.


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