AMD has officially released the first patch for the chipset driver, fixing the UEFI CPP2 driver that helps in assigning threads to the right workloads. The patch for the chipset driver can be found. AMD recommends all Windows 11 users install the update at the earliest. The other issue pertaining to the L3 cache latency on the Ryzen processors has already received a beta update, with the full-fledged release planned for coming Tuesday.
Earlier, the first Cumulative Update for Windows 11 had worsened the L3 latency issue on AMD Ryzen CPUs rather than fixing it. Unofficially dubbed “patch Tuesday”, Microsoft has scheduled Win 11 updates for the second Tuesday of every month. According to results posted by TPU, the L3 cache latency before the first Tuesday update was 17.1 ns. After the update, this figure grows (by more than 50%) to 31.9 ns!
This bus is known to affect all Ryzen CPUs, from the 2nd Gen Zen+ to the latest Zen 3-based Ryzen processors. The L3 cache latency deteriorates by as much as 6 times, adversely affecting the lows in games. Certain latency-sensitive games reportedly show a deficit of as much as 15% in some cases.
|Measured and functional L3 cache latency may increase by ~3X.
|Applications sensitive to memory subsystem access time may be impacted. Expected performance impact of 3-5% in affected applications, 10-15% outliers possible in games commonly used for eSports.
|A Windows update is in development to address this issue with expected availability in October of 2021.
|UEFI CPPC2 (“preferred core”) may not preferentially schedule threads on a processor’s fastest core.
|Applications sensitive to the performance of one or a few CPU threads may exhibit reduced performance. Performance impact may be more detectable in >8-core processors above 65W TDP.
|A software update is in development to address this issue with expected availability in October of 2021.
AMD had released a statement on social media stating that patches for the two issues have been developed, and will be released soon. The patch for the Preferred Cores (UEFI-CPPC2) bug will be released on the 21st of October, while the L3 cache latency bug will be fixed via a future Windows Update scheduled to roll out on the 19th of October.