FPS Limiting questions

[micstatic 4,316]

Hi All.  I currently run at 60hz 4k with unlimited game FPS limit, VSYNC on, TB on.  

1.  If I were to change my monitor to 30hz which is possible and use an external limited like nvidia inspector to cap at 30hz, does that mean you actually see a performance improvement since processor doesn't have to work as hard?  Or does it just literally prevent any FPS over 30 and get more smooth performance.  I'm really struggling to put this question into words.  But I'm wondering if limiting the FPS just benefits the system by preventing spikes and dips which we perceive as a studder, or if limiting actually runs the machine slower allowing better performance for other tasks.  

 

2.  I don't see any FPS limiter option in Nvidia control panel.  So does that mean I have to also use Nvidia Inspector?  I'm confused how these would play together as some of the settings appear in each.  Haven't used inspector since my FS9 days, but want to experiment with capping FPS.  

 

Thanks. 

[Rogen 1,087]

Hi micstatic,

 I think you're confusing the use of 30 hz.

If you run your monitor @ 30 Hz you can enable vsync in P3D and video output will syncronise to the 30 Hz monitor mode.

Which will give you 30 fps, no need for a limiter at all as vsync @ 30 Hz = 30 fps.

Plus it will be ultra smooth.

 

There's lots of posts on using 30 Hz or using 60 Hz and a halfrate sync should you have a monitor that cannot do 30 Hz.

https://www.avsim.com/forums/topic/560928-p3dv45-micro-stuttering/?do=findComment&comment=4078536

Cheers 

[micstatic 4,316]

Thanks for my reply. But I was under the impression the internal limiter doesn’t not work properly. 

[Rogen 1,087]

Hi micstatic,

There is a quite huge difference between limiting the frame rates and using VSync, although I can see why there would be confusion between the two.

While VSync does limit frame rates, it does it so by synchronising to the monitor refresh rate, hence 30 Hz equals 30 fps max.

Because P3D and the monitor are in sync the display is really smooth and given P3D and the GFX card have a maximum cap of 30 fps, you'll be able to ramp up the GFX settings to make far better use of the GFX card for a more imersive and better performing sim.

In P3D you set the Target Frame Rate to Unlimited, Vsync On and Triple Buffering ticked.

Your rig also needs to be able to output @ least 30 fps anyway, i.e if you can only get 20 fps vsync is of no use because vsync won't happen until the frame rate able to be output is equal to or higher than 30 fps.

On my rig if I disable vsync i get ~45 fps, this means I have headroom for when P3D hits a rough patch and the fps drop.

 

Also you can use the P3D internal frame rate limiter but it won't reliably hold the rate you've set.

What I found is that if you want to use the P3D rate limiter you'll need to tweek the prepar3D.cfg

[DISPLAY]

TEXTURE_BANDWIDTH_MULT=960

TEXTURE_BANDWIDTH_MULT=30 is the default and what I did was experiment by increasing it's value till I saw no appreaciable change in fps improvment - 960 was that value. Note this value is subjective and works for me.

Now if I wish to use P3D's internal limiter it is able to output the value I've set the slider to.

Do a bit of searching and check out the other posts, there is a lot that's already been written regarding 30 Hz, vsync and limiting frames.

Cheers

Edited December 6, 2019 by Rogen

[micstatic 4,316]

The monitor I have doesn’t support vsync. Just was talking about the P3d vsync setting. Eager to hear what others say about inspector vs control panel settings. Thanks rogen

[Bob Scott 7,716]

51 minutes ago, micstatic said:

The monitor I have doesn’t support vsync. Just was talking about the P3d vsync setting. Eager to hear what others say about inspector vs control panel settings. Thanks rogen

You're confusing Vsync with G-Sync.  VSync is not a monitor function, it is a software function in the OS, application, and/or video driver that synchronises the output to the monitor's fixed hardware refresh rate.  G-sync is a variable refresh rate technology that requires a hardware interface in both the video card and monitor.

[Rogen 1,087]

1 hour ago, micstatic said:

The monitor I have doesn’t support vsync. Just was talking about the P3d vsync setting. Eager to hear what others say about inspector vs control panel settings. Thanks rogen

All monitors support vsync because it's not a function of the monitor.

And I use NVidia inspector myself but not to limit frames. Inspector provides access and control to more advanced functions of the GFX driver that you normally are not able to access via the NVidia control panel, things like Silk Smoothness and more control over AA and filtering.

Anyway your original post mentioned 60 Hz with vsync on, do you actually get 60 fps? because you would need to get at least 60 fps for vsync to kick in.

Is the monitor actually capable of a 30Hz screen mode?

 

If so the best thing is to try a 30 hz vsync yourself.

Set your desktop to a 30Hz screen mode, my monitor does 1920 x 1080 @ 60, 50, 30, 24, 23 Hz as well as all the DSR UHD modes.

I set the screen mode using NVidia control panel.

And in P3D set the Target Frame Rate to Unlimited, Vsync On and Triple Buffering ticked.

As long as P3D is actually able to output at least 30 fps you'll have vsync.

Cheers

Edited December 6, 2019 by Rogen

[micstatic 4,316]

thanks will play around with it.  I use a samsung 4k tv.  Yes it's capable of 30

I just wanted to try locking externally as I only want P3D to run 30.  I don't like having the mouse lag in other windows functions. 

Edited December 7, 2019 by micstatic

[Rogen 1,087]

41 minutes ago, micstatic said:

thanks will play around with it.  I use a samsung 4k tv.  Yes it's capable of 30

I just wanted to try locking externally as I only want P3D to run 30.  I don't like having the mouse lag in other windows functions. 

OK, completely understandable.

So what I have configured is to launch P3D, the display then automatically swaps to the 30 Hz mode, and when I shut down P3D the display reverts back to a 60 Hz mode.

This thread below by MadDog has all you need to set it up and I can say it works just fine.

My main P3D monitor runs @ 30 Hz only while P3D is running and my other two run at 60 Hz for other fuctions like little nav map, web browser, Active Sky etc.

 

Addendum: Another option is RivaTuner Statistics Server, it's an app that can limit frame rates directly or trigger a half rate vsync, so P3D can run on a 60 Hz screen mode and yet still vsync @ half 60 hz for 30 fps. There are quite a few threads on it.

Edited December 7, 2019 by Rogen

[micstatic 4,316]

thanks again.  30hz seems to be working better.  I tried your Display changer idea.  Only problem.  I entered in the target of the p3d icon:

D:\DisplayChanger\dc2.exe -configure="D:\DisplayChanger\P3D30HZ.xml" "C:\Lockheed Martin\Prepar3D v4\Prepar3D.exe"

When I attempt to click the icon i get a Display Changer II window that says

An error occurred when starting the application. (Error Code 0x2e4).  The command line is:

"C:\Lockheed Martin\Prepar3dv4\Prepar3d.exe"

[Rogen 1,087]

Assuming paths are all good as is the P3D30Hz.xml you would have created, try elevation.

 

[micstatic 4,316]

got it figured out.  Even though I had run as administrator checked I had to go in the advanced section and check that too.