A recent Windows update is causing turmoil in the gaming community: patch KB5066835 It is strongly suspected that a number of systems massive drop in performance Leading in games. Initial analyses point to losses, In extreme cases, More than 50 percent should amount.
The suspicion: Significant losses in e.g. Assassin’s Creed Shadows
The first indications of the problem came from the community itself. Users Reported Suddenly Unusually low frame rates (FPS) in titles such as Assassin’s Creed Shadows.
These observations were made by an Detailed analysis of Digital foundry hardened.
The tests were carried out on an High-end platform with one Ryzen 7800X3D and one RTX 5090 carried out. The result is shocking:
- On one unpatched Configure the system in the affected scenes Significantly higher frame rates have reached.
- On the Identical system with installed KB5066835 Some of them were only half as high FPS measured (e.g. about 34 FPS compared to more than double).
A difference of this magnitude is highly unusual and pointing to a profound bottleneck in communication between Windows components and graphics hardware.
However, Only Nvidia is affected: According to current knowledge (as of 27 November 2025), only users with Nvidia graphics cards affected by the loss of performance. AMD and Intel users seem to be spared.
More than just a game: Counter-Strike 2 and other issues
The effect should be in Multiple play situations reproducible This is what underpins the thesis of a systemic problem. Also in the popular shooter Counter-Strike 2 Described to individual users more restless presentation, albeit without robust readings.
Neither Microsoft still Nvidia So far, they have officially announced which games or system configurations are potentially affected.
Nvidia responds with hotfix
Shortly after the first reports has Nvidia reacts and an Special hotfix provided. Preliminary comparisons suggest that this hotfix reflects the observed fluctuations, especially in situations with high GPU utilization. at least partially mitigated.
What is the cause of the loss of performance?
The real cause of the massive performance losses is still unexplained. There are several assumptions:
Changed routines: Microsoft may have internal Operating system routines have adapted, which have a negative impact on unforeseen rendering processes.
Or even a driver conflict: The update could be an pre-existing conflict with current graphics drivers only made visible have.
Other conceivable cause: I have also read that in certain cases between the game, the Desktop Window Manager (DWM) and the graphics card creates a communication error and thus causes disturbances in the rendering of the games.
An additional indication of deeper system interventions is that after installing the update in the Windows recovery environment (Recovery environment) partly USB input devices not detected became. Although this issue appears independent of gaming performance loss, it suggests that the patch Deeper in the system Assumed as usual.
Conclusion and outlook
This Windows update KB5066835 has the potential to drastically degrade gaming performance on some high-end systems.
Until Microsoft or Nvidia Further information, an official statement or a correction, the situation remains unclear. If you are currently struggling with massive FPS burglaries, check if the Hotfix by Nvidia is available for your configuration and at least reduces the problem.
TL:DR
I would recommend that you first Nvidia Hotfix check, as this should restore the performance without jeopardizing the system security. If that doesn't help, uninstalling the update KB remains the last option.
But that's it! Important note for uninstalling: KB5066835 is a Security update. The uninstall fixes the performance problem, but at the same time exposes the vulnerabilities that were closed by this update.
Have you encountered similar issues after the KB5066835 update?
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