Update 10/21/21 10 am PT: Microsoft has now released the Windows 11 patch to the general public. This patch contains the fix for the second bug that cause the L3 cache latency and bandwidth issues. That means that both required fixes are now available for AMD processors. We have amended the text below and added the relevant line from the Windows changelog to the end of the article.
AMD has also confirmed to Tom's Hardware that it has released a patch for one of the two bugs that lead to reduced performance in Windows 11 and impact the Best CPUs for gaming. The first patch comes from AMD in the form of a chipset driver that fixes the UEFI CPPC2 driver that's responsible for steering threads to the correct cores. Naturally, all users on Windows 11 platforms should update to the new patch immediately — you can find the new driver here. The second patch comes from Microsoft as a Windows update that arrived today. As a reminder, the bugs impact all Windows 11-compatible AMD processors.
The first patch fixes AMD's UEFI CPPC2 (Collaborative Power and Performance Control 2) feature, also known as the 'preferred core' technology that helps steer lightly-threaded work to the fastest cores on the chip. This bug primarily impacts performance in lightly-threaded applications. AMD says the performance reduction may be more noticeable in chips with more than eight cores and a >65W TDP rating, but the patch released today will correct those issues. We have the changelog listing below.
The second patch, which Microsoft has released as the 22000.282 (KB5006746) Windows 11 update, fixes an L3 cache error that impacts latency and bandwidth. As you can see from our deep-dive testing last week, we found that, before the fix, AMD's L3 latency can be as much as six times higher in Windows 11 compared to Windows 10. Additionally, L3 bandwidth can be up to 12X higher in Windows 10.
AMD says the L3 cache bug can reduce gaming performance by up to 15% in some eSports titles and 3-5% in desktop PC applications, though we didn't see such a severe impact in our own gaming tests. Microsoft originally released the new Windows Update to its Insider program, but it is now available to the general public through the standard update process. Here's AMD's graphic that explains both patches:
The bugs couldn't come at a worse time: Intel is on the cusp of launching its seemingly potent Alder Lake chips that will undoubtedly tighten the race for desktop PC supremacy. Making things worse for AMD, Windows 11 has new scheduler optimizations specifically for Alder Lake, so reviewers will use the new operating system for testing. That raised concerns that the bug could possibly result in unfair comparisons, particularly if the second patch didn't arrive in time for reviewers to incorporate into their launch-day testing for Alder Lake. The availability of both patches allays those fears.
Both bugs impact every Ryzen CPU supported in Windows 11. That means all Zen+, Zen 2 and Zen 3 CPUs that comprise the Ryzen 2000, Ryzen 3000, Ryzen 4000, and Ryzen 5000 processors. In addition, select AMD EPYC processors for data centers and some newer Athlon chips are also impacted.
As mentioned, we've already shared plenty of performance testing that shows the impact of the Windows 11 bugs. We'll circle back with updated testing soon.
Here's the AMD and Microsoft changelogs on the respective updates:
AMD Chipset Version 3.10.08.506 Changelog:
- AMD Chipset Drivers
AMD Ryzen™ Power Plans (required for UEFI CPPC2 support with “Zen+” and “Zen 2” in Windows® 11)
AMD Ryzen™ Power Provisioning Package (required for UEFI CPPC2 support with “Zen 3” and later in Windows 11)
Microsoft Windows 11 22000.282 patch (KB0006746) Changelog:
- Addresses an L3 caching issue that might affect performance in some applications on devices that have AMD Ryzen processors after upgrading to Windows 11 (original release).
- You can see more of the changelog here.