PMDG Stutters - 737 & 747

[Daniel Baker 20]

Hi,

 

I'm using P3Dv5.3 on windows 10 and I've noticed a strange issue with my PMDG 737 and 747s when taxiing on the ground before take-off.  I get something like a micro-stutter (maybe a long-frame? Heard that expression before) every 2-3 seconds or so.

I have my v-sync set in the nVidia control panel to Adaptive (half-refresh rate) on my 60 Mhz monitor to achieve a stable 30 fps in P3D, with v-sync off in P3d and frames set to unlimited.  This gives me a stable 30 fps in every other plane (FSlabs, iFly, PMDG 777, CaptainSim, etc.)  Weirdest thing about it is that it seems to resolve on landing.

I don't have FSUIPC logging enabled, I turned off sound preloading in the PMDG aircraft options.

 

Any ideas what else could be causing the issue?

 

Thanks,

Daniel

[Bob Scott 7,721]

System specs?

What does GPU and CPU core loading look like while this is happening?  Daytime or nighttime?  Weather?  At all airports or a particular one?

[Daniel Baker 20]

31 minutes ago, Bob Scott said:

System specs?

What does GPU and CPU core loading look like while this is happening?  Daytime or nighttime?  Weather?  At all airports or a particular one?

Hi Bob,

 

Thanks for your input.  Specs:
Processor    Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz   3.70 GHz
Installed RAM    32.0 GB (2747 MHz)
System type    64-bit operating system, x64-based processor
Edition    Windows 10 Home
OS build    19045.3803
GPU   nVidia RTX 3090
Driver 546.33

 

All weather scenarios (using ActiveSky P3Dv5) and both day and night.  All airports.

 

Will put up a flight with the PMDG 737 to see about GPU and CPU core loading.

[Bob Scott 7,721]

A couple possibilities come to mind based on past experience with a similar configuration (8086K + RTX3090):

If you have dynamic lighting on with SSAA and have your taxi/rwy turnoff lights on, it can really slam the GPU and produce stutters.  I ran 4xSSAA with dynamic lighting off in daytime, and 4xMSAA + DL at night.  Having them on together was a bridge too far.  Acft that don't use DL for their taxi/RTO/landing lights don't tend to have that issue.

Could also be AI traffic related--try turning traffic off or down and see if the stutters persist.

[Daniel Baker 20]

CPU:
Seems like Core 1 is pinned at 100%

GPU:
Around 4%

5 minutes ago, Bob Scott said:

A couple possibilities come to mind based on past experience with a similar configuration (8086K + RTX3090):

If you have dynamic lighting on with SSAA and have your taxi/rwy turnoff lights on, it can really slam the GPU and produce stutters.  I ran 4xSSAA with dynamic lighting off in daytime, and 4xMSAA + DL at night.  Having them on together was a bridge too far.  Acft that don't use DL for their taxi/RTO/landing lights don't tend to have that issue.

Could also be AI traffic related--try turning traffic off or down and see if the stutters persist.

Okay will try these suggestions, thanks very much.

 

Still find it odd that it only happens with the 737 and 747 PMDG planes. 777 is fine.

I would think the FSlabs series would have a lot more going on, and it behaves very well.

[Bob Scott 7,721]

You might try turning VSync on in P3D with half-adaptive rate set in NCP and unlimited still set in P3D's settings.  When the P3D frame rate is moderated by VSync, lookahead frames are no longer produced, and you should see the main thread core (core 0 unless you configure it otherwise) averaging somewhere more like 75-80%.  When it's pegged out at 100%, you're in the stutter zone.

BTW, are you running with hyperthreading on?  If so, adding an affinity mask is important to fence off, at a minimum, the paired virtual CPU on the core running the main thread.  An AM of 1365 (0x555 or binary 010101010101) will restrict P3D from running on the 8700K's HT virtual CPUs.  P3D with HT off requires no AM, and was considerably smoother with my 8086K.

[Daniel Baker 20]

Okay V-Sync in P3D did not unpeg Core 0, unfortunately.  Tried with triple buffering and that didn't help either.

I think hyperthreading is on, because I see 12 cores instead of 6 in the task manager - I think that's the indicator, right?  I could swear I had set that to off at one point - something must have reset.  On next boot I'll remove it.

[Bob Scott 7,721]

I did some reading on adaptive V-Sync, and I now believe that's a considerably different proposition than using fixed 1/2 refresh rate VSync like you'd get by setting it with nVidiaInspector.

As I understand it, adaptive V-Sync just turns regular v-sync on and off based on high/low frame rate thresholds--what you need is a constant 30Hz sync rate at the driver level.  That can be forced with NVI, and I believe it's also possible with MSI's Afterburner/Rivatuner utility suite.

The magic combo for me over years now is running VSync-limited to a hardware-enforced 30Hz refresh rate, and frame rate unlimited in P3D.  In my case, I have a 55" 4K TV that will natively accept a 30Hz input, so I can just set the refresh rate to 30 in NCP and then turn V-Sync on with frames at unlimited in-sim.  With a monitor that only allows a fixed 60Hz refresh rate, you have to use the aforementioned driver-level intervention to lock at 30.

[jcomm 5,939]

8 hours ago, Bob Scott said:

With a monitor that only allows a fixed 60Hz refresh rate, you have to use the aforementioned driver-level intervention to lock at 30.

Interesting explanation of how "Adaptive" works... 

Regarding the "aforementioned driver-level intervention", are you referring to this, or to the option to lock the frames at 30 FPS, both in NVI orr NCP ?

[Bob Scott 7,721]

8 hours ago, jcomm said:

Interesting explanation of how "Adaptive" works... 

Regarding the "aforementioned driver-level intervention", are you referring to this, or to the option to lock the frames at 30 FPS, both in NVI orr NCP ?

I'm referring to setting the refresh rate to 1/2 the monitor's hardware refresh rate at the driver level--that's done by writing registry settings for the graphics system using a utility like nVidiaInspector or Rivatuner. 

[jcomm 5,939]

1 hour ago, Bob Scott said:

I'm referring to setting the refresh rate to 1/2 the monitor's hardware refresh rate at the driver level--that's done by writing registry settings for the graphics system using a utility like nVidiaInspector or Rivatuner. 

Ah! Ok, not the "Adaptive half...". Right !!!! I'll try it that way. Thx !

[jcomm 5,939]

I  noticed that VSync effects differ between P3Dv5 and v6.

In V5 if you don't set VSync in sim, and set it in Nvidia Control Panel (NCP) or Nvidia Inspector (NVI) you get the refresh rate of your monitor more or less stable in the sim when you use SHIFT-Z to see the "simulation parameters" but in v6 setting only in NCP or NVI doesn't work the same way and the FPS counter will vary as if no Vsync was set. 

In P3D v6 VSync must also always be set also in sim if we want it's effects to work, at least until one of the last patches before 6.1 .

When I set it in NCP or NVI instead of in sim I did it because I was told it would hammer the CPU less than setting it in sim (?)

Edited January 9 by jcomm