[NOTICE] Windows 10 1709 Fall Creators update halving FPS

[InstantAli3n]

ORIGINAL TOPIC SUBJECT: [B18 ONLY] FPS "sticks" at 1/2 refreshrate. Performance is not an issue.

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Initially the game will run at my Hz rate of 165 like it always has on my G-Sync monitor with Nvidia driver set to Prefer Maximum Performance for Rimworld.

After a minute or so it will drop to 83 and stay there. I can trigger it to go back up to 165 by alt tabbing a bit, zooming out, panning around, playing on fast forward, etc. But then it will shortly go back to exactly half of the max allowed fps.

Using an FPS limiter like RTSS and setting 164 (or anything else) results in the fps locking to half of that value. EG: FPS limit 60 = 30fps. This is not a vsync double buffer issue as far as I can tell either. How can it be when I'm using g-sync and limiting it below the max range!

This behavior just started to occur after B18, the only other system differences are upgrading from Windows 10 1703 to 1709 (new install actually) and from Nvidia 388.59 to 388.71.

I cannot find a workaround with any driver, game or OS settings (something I'm passionate about).

The UI is noticeably laggy at half refreshrate, panning is much blurrier, and honestly it's just a much smoother experience at 164fps rather than 82. So much so that I'm making a topic here in hopes of some insight/resolution/acknowledgement instead of playing. I'd love to help troubleshoot!

[InstantAli3n]

It's Windows 1709, nothing to do with Rimworld. I can see the same behavior in web browser vsync tests. Hopefully this will explain a lot of other peoples issues. (And be fixed soon). I will post again if I find a reliable workaround.
https://www.reddit.com/r/Windows10/comments/79utn0/fall_creators_update_build_1709_causing/

[InstantAli3n]

The bug has been patched by Microsoft with the February 13, 2018 update. KB4074588
OS Build 16299.248

https://support.microsoft.com/en-us/help/4074588

Addresses issue where, in certain hardware configurations, the frame rates of DirectX Games were unintentionally limited to a factor of the display's vertical synchronization.