Big FPS impact when using internal FPS limiter

[touchdown84 34]

Hello!

Is it just me or why does the internal fps limiter such an impact on the fps?

For example when I'm running ~40 FPS @ unlimited and then set the limiter to 60 the fps drop to 30. And when I set the limiter to 30 the fps drops further to 25. Basically I won't get the fps I set, even though running at a higher limit or unlimited clearly shows it's capable of running at that value.

I tried to limit the fps as it feels like it has a positive impact on blurries and a slightly reduce in VAS, but that could also just be because it lowers the fps in the way I described.

 

Jan

[downscc 1,327]

You got something else going on there.  I limit to 20 and it runs an average 19.3, and I had equivalent values at 24 and 30 fps.

 

It is not the frame rate limit causing the variance.

[Dirk98 354]

When you set anything but unlimited fps in P3D there is FPS impact as the engine starts buffering some frames ahead (or something along these lines). Therefore the best settings/hardware combination is to use unlimited with VSYNC on in P3D settings, and set your montor's Vertical to 30Hz (I use 25Hz). You'll get the best performance and fluidity. Limiting fps in nVidia Inspector (vs. monitor's setup) doesn't work as good unfortunately.

 

Dirk. 

[downscc 1,327]

 

 

Therefore the best settings/hardware combination is to use unlimited with VSYNC on in P3D settings, and set your montor's Vertical to 30Hz (I use 25Hz).

 

Okay, that's an opinion.  I wouldn't claim it to be the best regardless of system configuration and hardware.

[edpatino 1,960]

You got something else going on there.  I limit to 20 and it runs an average 19.3, and I had equivalent values at 24 and 30 fps.

 

It is not the frame rate limit causing the variance.

 

Think this is correct. Look for something different!.

Cheers, Ed

[Forkboy2 27]

My understanding is that enabling internal FPS limiter also enables Fiber Frame Time Fraction.  Try lowering FFTF to 0.01 if you're going to use internal FPS limit.

[touchdown84 34]

My understanding is that enabling internal FPS limiter also enables Fiber Frame Time Fraction.  Try lowering FFTF to 0.01 if you're going to use internal FPS limit.

That could be the problem. I got conflicting statements on this (some say FFTF is only active whit internal limit, others say it is ignored whit internal limit, but most posts on this are rather old and for FSX).

With my new PC I could finally crank up all settings to the max and still maintaining over 30 FPS (unlimited) even in very demanding situations (actually I now have to tune settings down quite a bit because I'm getting VAS related OOMs even though fps are high and smooth).

But the default 33% FFTF could be shifting the load in the wrong direction, I'll try that this evening.

[SteveW 1,792]

The fps slider in P3D Display settings (or FSX) internal fps setting is not a limiter. fps continues to run at unlimited until the look-ahead buffer, default 3 frames, is filled, and then fps output relents. If the system can maintain a look-ahead buffer, each frame will be produced such that the aircraft and the terrain will appear in the correct position. The physics of the sim is accurately maintained since each next frame is genuinely built for a particular point in time say 1/30s precisely. Without the look-ahead buffer, each next frame is built depending on how long it took to build the last frame, if the fps is not maintained with an even period this never puts the aircraft and scenery in the place computed for. The VSync setting in P3D Display Settings enables the GPU to maintain consistent fps by limiting the fps at the refresh frequency of the monitor. As Dirk correctly points out this generally offers very good results with most systems. Also this way does not require such high performance, setting the fps slider requires the best performance possible from the PC, and is really only useful at 60 or below fps since above that the time between frames is very small. This P3D VSync setting does not control tearing on screen, vsync for that is tied to the Windows Desktop refresh since P3D only displays within a desktop DX11 window viewport, the fullscreen mode is merely a screen sized window with no border or caption. Whatever is chosen fps slider position or unlimited, makes no difference to FFTF and so on, a limited frame-rate is easier to put into a formula than a constantly changing fps, and so to take it as meaning "works with Frame Lock only" is a mistake.

[SteveW 1,792]

...those with high frequency monitors can still try it out, with NVidia cards we can create custom monitor profiles in the NVidia Control Panel, and experiment with different refresh frequencies and the use of P3D VSync and Triple Buffer with Unlimited on the slider. Try fractions of the real refresh frequency say 20 or 30 with a 60Hz monitor (1/2 , 1/3) or 24, 29, or 36 with a 144Hz monitor (1/6, 1/5, 1/4).

[RaptyrOne 1,398]

Is there any chance that a monitor could be damaged if we run a custom profile that forces a 60 Hz monitor down to 30 Hz?

[SteveW 1,792]

None I can think of with current technology digital panels dvi hdmi and displayport.