Microsoft released the first Cumulative Updates for Windows 11 on October 12th. AMD and Microsoft discovered shortly after the release of Windows 11 that the OS is not optimized for AMD Ryzen CPUs, resulting in higher L3 cache latency and a broken UEFI-CPPC2 (preferred cores mechanism).

Testing revelas a close to 20 ns L3 cache delay for some Ryzen processors. The October 12 "patch Tuesday" update increased that value even worse reaching 30 ns.

AMD made a remark on social media that was shared on Reddit. The company stated that fixes for the two bugs are being developed and will be available soon. On October 21, the UEFI-CPPC2 bug patch will be released. AMD's "customers" include huge organizations who use Threadripper or EPYC workstations to conduct mission-critical workloads. On October 19, Windows Update will fix the L3 cache delay bug.

New Windows 11 Patch Worsens Ryzen L3 Cache Latency, AMD Announces Fix Dates