Windows 10 - Alt-tabbing 'breaks' double buffering - why?

[Frame Paced]

This is a version of a post I made on Nvidia's forums, think this forum might be more applicable (?).

I find that in many DX9/DX11 games, if the game has a hard double-buffered vsync implementation in place (eg: when the framerate can't maintain 60, it drops hard to 30), after loading it, then alt-tabbing to the desktop and back in the game, enables a form of triple buffering, allowing the framerate to drop to 59/58fps without huge drops to 30. For many games where I'm on the cusp of a solid 60 the majority of the time, this is actually preferable.

However, there are times when this is not desirable. Triple buffering can introduce noticeable input lag, but as well can have issues with frame pacing. This is especially noticeable for some games where I want a consistent 30fps. For a game where you're usually well above the performance required for a solid 30 but also below 60, I'll sometimes prefer a good 30fps lock instead of a fluctuating framerate. This seems to affect the entire Batman Arkham series, in particular Arkham Knight which I play at 4k/30 on my 1660 (I can never get a stable 60 without some stutter, plus it looks so good at 4k). Starting up the game for the first time and I get a nearly perfect 30fps lock with solid framepacing.

However, once I alt-tab out and back again (which I can do often during long play sessions to check email or research a hint if I get stuck), even if I set the in-game limiter to 30fps, the frame pacing is brutal - tons of judder even though Rivatuner is reporting a solid 30. There's also noticable controller lag. I can try to limit the fps with Rivatuner/Nvidia half-rate refresh from the outset, but there just not as good as double buffered. Only way to fix it if I forget and alt-tab is to quit and reload the game.

So...anyone knows why this happens? Is this a game engine issue or something Nvidia has purposefully implemented in their drivers, or a Windows quirk that can't be avoided - or a combo of all three? If a game doesn't have a native triple buffering option I'd like for it to stick with the developers wanted, or at least not make it so easy to break (triple buffering can be forced in other games using fast-vsync, d3doverrider, etc). There are also some games - like Rise of the Tomb Raider - which I could have sworn earlier had working double buffering before, but now always triple-buffers regardless of the setting in the game or even if you don't alt-tab.

I'm actually wondering if this is why Rivatuner's 30fps cap 'stopped' working effectively in providing good frame pacing, at least from what I've gathered by older threads on the web - somewhere around Win10's lifespan (?) it interfered with a games buffering mechanism and introduced stuttering, at least that's been my experience with just setting a 30fps cap, I've never gotten good framepacing with it.

[RealNC]

Sounds like a bug somewhere. The game, driver or OS.

[Zinohh]

I would download PresentMon from GitHub and see if Alt+Tabbing is breaking the exclusive fullscreen mode of the game.

[AddictFPS]

Zinohh +1

This smells like when open game apply FullScreen, and ALT+TAB force game to Windowed Minimized, and when join game again is just Windowed Maximized, not FullScreen.

In some games, when you press ALT+ENTER can change betwhen Windowed/FullScreen and fix this.

In Windowed state, the game is just one more window in your desktop, and this can cause several issues like you describes here. The base of problems are the Windows Desktop Composition feature, has some limitations.

Another fix can be open the game console and type the command to restore FullScreen.