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VAS and Performance tips!


Dave Hoffman

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Dave Hoffman

Hello all,

I'm a new customer to FlightSimLabs, and I'm not disappointed.  I have use both the boxed versions of FSX, and FSX-SE, and am now running Prepar3D and trying not to look back.  Over the years, and in conference with a friend of mine who is also an avid simmer, I have discovered some performance enhancing techniques for your sim.  Some of these can be easily found on the internet, but here, I am going to focus on P3D, and without getting too specific as to my system settings.  The reason being that P3D is more stable than FSX, and is delicate, but more fault-tolerant.  I've got a LOT of stuff installed on it and I'm getting incredible performance, including with the A32X. 

 

  • Hyperthreading:  If you use a processor, either Intel or AMD, and it's capable of running more than one thread per core, the best thing you can do is TURN IT OFF!  You heard right.  Hyperthreading or multithreading is great for running a bunch of desktop applications in a more harmonious manner, but we're talking about an engine that was developed for use with single-core processors.  Do a test with the A320 at an addon airport with your sim "fully loaded" at a gate, then go into your BIOS and turn off hyperthreading, and try the EXACT same setup again, and you'll have to pick your jaw up off the floor with the memory you will save. 
  • Frame Limiter:  I'm no hardware expert, but from what I understand of frame limiters, they work on the level of microscopic time and ultimately smooth out the performance that you are getting by doing the following.  Frame limiters save the time of outputting frames they otherwise would have had they not been limited, and allocate those nanoseconds to doing other processes, ultimately smoothing your performance, and adding an element of scheduling to what your graphics card is doing.  30FPS is less than desirable in today's world, but a smooth 30FPS is very desirable in a flight simulator.  There is NO good reason to use the frame limiter inside ANY of these sims.  They do NOT work, so set them to "Unlimited."  Use a graphics card utility such as the NVidia Control panel to set application specific frame limits.  Use a frame rate that is right at, or half of your monitor's refresh rate.  Mine's 60, so 60 or 30 would be applicable to me.  Vertical sync should be on in the application to eliminate tearing (visible when viewing a whirling propeller).
  • SLI/CrossfireX:  I've got two video cards in my rig, and love the performance of having a second GPU doing some of the work.  However, the application engine was developed before this technology came to be fruitful.  Using SLI in P3D or FSX is basically a placebo effect.  You will barely notice any effect in P3D, and it is also said that it can DECREASE performance in FSX.  If you have an NVidia card, you can change the application specific setting "SLI Rendering Mode" to "Single GPU"  Setting it this way also eliminates flickering of lights, smoke, and soft particles.  It also helps in OBS if you're a streamer.  Using SLI will cause OBS to render only half of your frames, so your broadcast will be choppy.  If you're broadcasting at 30FPS, the app will run at 15 and look more like a slide show.  Remember, SINGLE GPU!
  • AffinityMast tweak:   With regards to .CFG tweaks, less is more with P3D.  With P3D and FSX-SE, use the double-slash "//" to comment out the affinitymask tweak.  P3D and FSX-SE do a pretty good job of selecting the processors they want to run on, often you will get better performance NOT using the tweak. 
  • .CFG tweaks: Again, less is more.  Try these: 
  1. Under [GRAPHICS], set TEXTURE_MAX_LOAD=2048.  This is a reasonable compromise between full HD and looking like dog food. We'd all like to be able to fly in 4K, but not with these sims.  Don't let any installers change that value when offered.
  2. Under [DISPLAY], TEXTURE_BANDWIDTH_MULTI=40.  Some guides have you set this higher, and to be honest, it has been my personal experience that the higher I set this, the more blurries I get.  I always thought it increased a multiplier of some kind and therefore, texture throughput, but this is what helped me.  YMMV.
  3. Under [MAIN], FIBER_FRAME_TIME_FRACTION=0.33, this is the default value.  Some guides recommend setting this to 0.01 to increase frame rate.  What this does is allocate a portion of the process's thread time to rendering texture.  If you want to get rid of blurries, keep this at 0.33.  DO NOT SET IT TO ZERO.  But, play with it, YMMV.  I've found blurries the lower I set it, and found no value to setting it higher.  Placebo? 
  4. Under [TERRAIN], TERRAIN_MAX_AUTOGEN_TREES_PER_CELL=4500, try reducing to 3000.  TERRAIN_MAX_AUTOGEN_BUILDINGS _PER_CELL=3000, try reducing to 2000.  May save you some VAS, and you won't notice much difference. 
  • Sliders:  The VAS killer is Level of Detail radius.  P3D is good at exceeding what FSX can do with the slider.  FSX Max right position was LOD=4.50, P3D is higher.  The farther to the right you slide this, the more miserable your VAS usage will be.  Keep it moderate.  Mine is a 5.5, but comes down for graphics preset when flying the 'Bus. 
  • If you can't read taxiway markings: such as in ORBX sceneries that use photoreal technology, sliding this up to 15 or 7cm per pixel will help alleviate this, and won't cost much VAS. 
  • Autogen: Both of these sliders can save you a little bit if you knock them down.  If you're flying a tube-liner then you won't be looking down at trees or buildings, you'll be busy managing the flight deck, only to get a quick glimpse out the window.  You can turn them down to the midpoint to save some overhead. 
  • Scenery Complexity: A note about this; you can turn it down to save some overhead, but if you're missing buildings or jetways at some airports, turning this up might help restore them. 

Finally, just remember these last few things with regard to scenery.  Like anyone that innovates, publishers try different things to be fhe first to bring something new to the market.  Sometimes they fail.  There are different sceneries from the same publisher that are sluggers when it comes to memory, performance, or both.  Some have hotfixes or updates, and some don't acknowledge there's even a problem.  Some refine their product, and some ask you to make concessions in other areas.  Personally, I'm still trying to work out how people can fly into JFK at a VATSIM event.  I have to offer a ritual sacrifice to the OOM gods to get into New York, in any airplane. 

Hope this helps, and happy landings. 

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If P3D/FSX "were developed for use with single-core processors" then how can they "do a pretty good job of selecting the processors they want to run on"?

Modern applications and games benefit from HT, for instance there are games where I have observed 15-20% frame rate increase with HT ON compared to HT OFF. Sure there might be issues if applications or games are unable to identify which core is physical and which one is logical. However, that's exactly when AffinityMask can be of use.

I have i7 2600k CPU and I have HT ON. Setting AM=85 (forcing P3D to use physical cores) significantly increases the frame rate especially in the most difficult areas impacting the performance the most.

I did some tests with Nvidia Inspector and frame limiter as well. As long as I am not using AM and P3D uses all 8 threads, the frame limiter is not affecting texture load times. If I use AM=85 and set frame limiter to ~25.4 in NVidia inspector then I have issues with texture loading times and lots of blurries.

I prefer having as large LOD as VAS allows. During the fair weather the difference between 4.5, 5.5, 6.5 (high, ultra and max respectively) is very noticeable at high altitudes.

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S_r_d_a_n  K_o_s_t_i_c
Quote

There is NO good reason to use the frame limiter inside ANY of these sims.  They do NOT work, so set them to "Unlimited."  Use a graphics card utility such as the NVidia Control panel to set application specific frame limits.  Use a frame rate that is right at, or half of your monitor's refresh rate.  Mine's 60, so 60 or 30 would be applicable to me.  Vertical sync should be on in the application to eliminate tearing (visible when viewing a whirling propeller).

Where is the setting in NCP for setting FPS? AFAIK, this can be only set with 3rd party utility, NI.

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And actually the question that was really bothering me was how does VAS usage depend on whether HT is on or off. I just did the test at T2G EDDM and I can report exactly the same VAS usage with HT OFF as I had with HT ON. The frame rate is exactly the same as using AffinityMask=85 I am loading the same cores.

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S_r_d_a_n  K_o_s_t_i_c

It's not a theory, but a hard fact in the sim community, and at least 10yrs old, if not way more. I've been around for quite some while (was it 1998 or about...).


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Norman Blackburn

Go further.  In fact right to the beginning of the humble IBM PC.  In order to be considered an IBM compatible PC it had to be able to run MSFS, 

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S_r_d_a_n  K_o_s_t_i_c

Oh yes. I think the first sim I've ever seen was something on the Spectrum ZX, loading it from the tape in a cassette deck :-)
But my FS was FS2000 really, briefly on FS98 if not mistaken. But my "career" if you want to call it that, began with FS9.


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Dave Hoffman
On 02/16/2017 at 2:36 PM, ai_ab said:

If P3D/FSX "were developed for use with single-core processors" then how can they "do a pretty good job of selecting the processors they want to run on"?

Modern applications and games benefit from HT, for instance there are games where I have observed 15-20% frame rate increase with HT ON compared to HT OFF. Sure there might be issues if applications or games are unable to identify which core is physical and which one is logical. However, that's exactly when AffinityMask can be of use.

I have i7 2600k CPU and I have HT ON. Setting AM=85 (forcing P3D to use physical cores) significantly increases the frame rate especially in the most difficult areas impacting the performance the most.

I did some tests with Nvidia Inspector and frame limiter as well. As long as I am not using AM and P3D uses all 8 threads, the frame limiter is not affecting texture load times. If I use AM=85 and set frame limiter to ~25.4 in NVidia inspector then I have issues with texture loading times and lots of blurries.

I prefer having as large LOD as VAS allows. During the fair weather the difference between 4.5, 5.5, 6.5 (high, ultra and max respectively) is very noticeable at high altitudes.

As with all tweaks, your mileage may vary.  This isn't a modern game, the engine was put on the market as FSX circa 2006, and from what I understand, originally only ran on one core.  One of the service packs enabled the affinity mask.  since LM has a license to modify the code (unlike Dovetail games), improvements can be made.  I personally gained a significant overhead increase with regard to VAS.  Others may not.  But, it's something to try...doesn't hurt. 

 

Agree on LOD radius though, as high as is practicable, but still a VAS killer. 

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Konstantin

Isn't the  FIBER_FRAME_TIME_FRACTION  tweak only effective if you use the internal FPS limiter?  A lot of people have noticed that limiting the frames internally reduces the performance, because the CPU is more busy with rendering the scenery. Setting the FPS to unlimited is akin to having FIBER_FRAME_TIME_FRACTION=0.01 with FPS limited internally, so I heard.

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S_r_d_a_n  K_o_s_t_i_c


Isn't the  FIBER_FRAME_TIME_FRACTION  tweak only effective if you use the internal FPS limiter?  A lot of people have noticed that limiting the frames internally reduces the performance, because the CPU is more busy with rendering the scenery. Setting the FPS to unlimited is akin to having FIBER_FRAME_TIME_FRACTION=0.01 with FPS limited internally, so I heard.



And that is quite right. This is why I tried a little combination, check out the thread in the General FSL forum.


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  • 2 weeks later...
Darren Howie

Your milage obviously may vary..

on my I7-7700 and Gtx1080 a limit of 40 worked perfectly at killing all stutters irrespective of frame rate.

Using Lasso to set Affinity added only a couple of fps if any however it did stabilize my fps to a nice steady 20-22 instead of a wavering 16-24 with continual large jumps and visual smoothness was maintained in heavy scenery and weather.

Woukd highky recommend anyone try the demo to see if it helps.

It did for me..

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