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Performance Analysis of recent fsx.cfg tweaks and GTX470

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Here's my experience of recent performance suggestions and an upgrade to Nvidias current technology. This game me a performance boost better than FSX DX10, but without any of the associated problems.

Software: Windows 7 64bit, FSX Acceleration, GEX USA and Europe, UTX Europe, REX2, FSPassengersX, Horizon VFR, UK2000 EGCC, FTX Australia, Captain Sim 727, and MyTrafficX 5.3! Others awaiting reinstallation time.

Hardware: i7-920@4Ghz, 6GB DDR 6-7-6-18@1600Mhz, GTX275 upgraded to GTX470@705Mhz, Dell 30” 2560x1600

The journey begins with two guides:



Initial results with my older GTX275 were good, but I could not get the performance improvement described without compromising image quality along the lines of DX10 mode. However an upgrade to the GTX470 enabled me to bring back the high levels of AA and AF that make all the difference. Just to be sure and because I'd lost control of FSX anyway, I did a complete reinstall starting with Windows.

When performance tuning, my goal is not to obtain as many FPS as possible, but rather to limit the maximum at 30 and try to stick around there. Occasional drops down to 25 or even 20 are OK and can be forgiven when the simulator is under stress and while that may cause tiny stutters the experience is not disrupted. Sometimes I fly with FPS locked, but usually unlimited with the FPS limiter especially at busy airports.

The highlights from my fsx.cfg are:


UsePools=0 or RejectThreshold=98786. On the GTX275 I used to have, UsePools=0 worked fine. However on the GTX470 that creates a lot of graphical glitches and crashes so I prefer to use RejectThreshold. There are still occasional “triangle flashes” but quite easy to live with.






AffinityMask=14. This puts the fiber infrastructure onto core 0 and the main FSX thread onto core 1. Core 1 is the one to watch for how busy FSX is concerning the CPU.



What about settings in FSX?

Everything to the right or check boxes checked except:

• Bloom

• Water Low 2X. If the scene allows (CPU overhead) it I will go Med 2X as I like the cloud reflections, but no higher as I find the autogen reflections too much.

• Aircraft Cast Shadows on the ground. Again if the scene allows (CPU overhead), I will check this.

• AI Traffic, 80-100% IFR. No GA, nor airport vehicles

• Road Vehicles about 10%, defaults on Ships and Leisure Boats.

Most of the time I run with frame rate unlocked with the FPS external limiter set at 30. Locking can work, but only over photoscenery away from major airports where the simulator is not stressed.

Performance Tuning.

I have both a CPU and GPU (GPU-Z) performance monitor to objectively tune the simulator to the scenario I am flying. If my FPS is 30, all is well and no attention is needed. If my FPS is being hit, typically it is because either CPU or GPU is being worked too hard.

GPU: If utilisation is 75% or more, the GPU may be the bottleneck. This is not true in every scene, but is a good rule on my system. I can reduce the consumption by:

• A smaller FSX window size; fewer pixels to render. I cannot always fly 2560x1600 full screen, so sometimes drop down to windowed mode when things are busy.

• Reducing the amount of cloud cover, either by changing the weather or reducing the cloud density significantly.

• Surprisingly, I found reducing the autogen made little difference to GPU utilisation.

CPU: My affinity mask puts the fiber infrastructure on core 0, the main FSX thread on core 1, and scenery and DTM builders on cores 2 and 3. Core 1 with the main FSX thread is the one to watch. With the FPS running unlimited (with external limiter), core 1 can run significantly below 100%. If that happens, I can turn up scenery elements if I choose to (either water mid 2x, aircraft shadows or more AI – they seem to affect CPU the most). If it is running at 100% and FPS is around 30, all is well balanced. If running 100%, and my FPS is suffering, I will start reducing the elements previously described to compensate.

The end result is one group of settings for the departure airport, another enroute and another for arrival customised to appropriate airports. Making settings changes is not a big burden at all, and easy with the FSX save settings capability.

Additionally I may have STB delete all the on ground aircraft in FSX except at the airport I’m arriving at or leaving from. For instance, at KSEA this deletes 200 other ground based aircraft (40-50 at KSEA itself remain) giving another significant performance boost. There will be some additional optimisation features in the next version.

Complex aircraft may require a little more compromise that the default Microsoft aircraft. The default B737 performs great in many situations. Fly the CS 727 instead with its complex (but very enjoyable) 3d cockpit and it may be necessary to turn down a few settings as described above. As far as I see, the greatest requirements of a complex aircraft is CPU, so turning down shadows or water can make the difference when necessary.

When experiencing “bad” FPS, it can often resolve if given a little time. We all understand the impact of moving jetways, but sometimes changes to the scenery settings can result in bad FPS for a few seconds before the simulator stabilises. So give it time to work things out before deciding a change is bad.

Results in FSX?

I can now do a whole lot of things in FSX that I never thought would be possible. I’ve made numerous flights with the default airports in KSEA, KORD, KDEN, KDAL to name a few and the experience is incredible. Memorable occasions including flying over the dense forests around Seattle with no loss of FPS, and the city of Los Angeles at dusk on the way to KLAX with autogen buildings filling virtually every position available on the ground texture. Payware quality airports such as UK2000 EGBB and Aerosoft Nice are no problem either. Just last night I flew into Nice with FPS locked at 30, all sliders as above plus shadows and water mid 2x!

The key to it is making some small adjustments to FSX settings according to where you are, what you are flying and the weather conditions. To spend a minute or two doing so in the context of an hours flight is no trouble at all.

Is everything perfect?

No, not quite! Can I fly out of EGLL UK200 with Aerosoft London VFR in a PMDG MD11 with all settings right? No, that is still too much. However tune the simulator as above and you can base yourself at Heathrow and have a good experience.

Even with NickN’s settings I still get more shimmers than I would like especially with scenery that is not mipmapped.

Sometimes there are performance drains that I cannot explain. For instance looking north out of EGBB I can drop about 8 fps but cannot see why. Even with the drain, I am still above 20fps so all is well.

I would say one more hardware upgrade is in order, when significantly better parts become than core i7 and GTX470 become available. That may be something for late next year.

In conclusion

The two websites mentioned at the start of this article and the 470 have made FSX into a new simulator. Whether it is GA or airliner flying that is your desire the BufferPools tweak in particular enables you to fly FSX as ACES imagined it could be one day.


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Good morning. I tried these settings ( and a bit more) on my system and want to share the results with you. System:

Intel I7-860, ATI 5770 GPU, 8GB RAM - so different CPU,GPU, memory and architecture.

This test was done in the approximity of Hahn airport, with approx 300 AI aircraft in the reality bubble, without AI I have excessive FPS (60+ with DX9, 200 with DX10 anyways). Only addon installed but MyTraffic VFR Germany 2010, so photo scenery with real world autogen. All sliders right but water, but there is no bigger water near to it

Switching back from DX10 to DX9 in this application brought almost nothing, because this is really a CPU limited example. Application of all the parameters made no change, frames always around 34, the only sensitve one is the CPU_Affinity, and this turned out to be very interesting.

14 binary 1110 leads to core 0 unused, at simulation startup core 1 is at 100%, 2 and 3 unused, 4-7 unused. Stable frames at 34. After 30 seconds, suddenly core 2 and 3 go up to 100% and remain there forever, and frames drop to 20-22.

Now I tried several other values:

15 binary 1111, at simulation startup core 0 is at 100%,1-3 unused, 4-7 unused. Stable frames at 34. After 30 seconds, suddenly core 1, 2 and 3 go up to 100% and remain there forever, and frames drop to 20-22.

17 binary 10001, at simulation startup core 0 is at 100%, 1-7 unused. Stable frames at 34. After 30 Seconds, suddenly core 5 goes up to 100%, but frames stay at 34!

Can this be understood? Maybe yes. If I understand right, hyperthreading generates the cores 4-7, with 4 being the logical partner of 0 using the same physical core. Now there are two effects:

if an i7 CPU only uses one physical core, it automatically overclocks by 266 MHz, so forcing one core to work only gives an advantage of 10% here. All the data are in the same cache, don't need to be exchanged between physical cores, saving a lot of overhead.

As I said, this may be very specific to the -860 which is maybe limited by its memory band width, and to the application which is dominated by AI traffic.

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Consider as a test switching off hyperthreading in the BIOS. I do not run with it, as for an overclocked i920 it adds nothing except heat and instability and does not improve my FSX experience.

The affinity mask affects the main scheduler, DTM and scenery agents only. It does not affect the fiber manager, on my system that still runs up to 10% on core 0. Since it has exclusive use (not competing with other FSX threads), that improves the stability of the frame rate and stutters.

Also try an area with autogen and set the weather to be overcast. That forces up the GPU load significantly, which is a scenario this tweak tries to address. KSEA is a good place for that!

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I see a vast improvement between 2.7Ghz default and 4.0Ghz on my i7 920 with a GTX285 1Gb and 12Gb of RAM running at around 1600Mhz and hyper threading is on. Temps are never a concern (usually max of 67c) as I have a huge Corsair 800D case with 5 PWM fans and a Noctua NH-D14 CPU cooler with a further 2 PWM fans on it too, 1 of which has been upgraded to the same Akasa Apache Black PWM fans used in the rest of the case.

The motherboard changes fan speeds for all fans depending on CPU load and temperatures, so its ultra quiet when doing nothing in particular and cool and relatively quiet when under 100% load, the GTX 285 fan is still the loudest fan in the case even when the CPU is at 100% load and the GPU is loaded too. I was going to go down the water cooled route, but I bought the only GTX 285 on the planet that you cant get a water block for, thanks ASUS :lol:

I don't bother with any tweaks really apart from the HIGHMEMFIX which I don't think I really need anyway. I do use an external FPS limiter and that keeps my frames locked at 30. I also try not to have more than about 270 AI in the reality bubble and I don't bother with road traffic or airport vehicle traffic either as these drain FPS massively, usually about a 30% drop even with the road traffic sliders at less than 8%, it's even worse if you use UTX Europe which I don't use anymore at all.

Water is usually at 2.x low, aircraft ground shadows on. Aircraft cast shadow on self, bloom and lens flare are always off. I never bother with DX10 either. All the rest of the sliders are to the right except autogen which is usually at Dense or Very Dense. The cloud distance slider varies depending on whether I'm low and slow VFR (60 miles) or high and fast IFR (90 miles). The cloud slider is not as much of a concern with Nvidia cards as it is with ATI cards, ATI really cannot handle heavy cloud situations very well at all, this is still the case even now with the latest line of ATI cards, which is a shame as I really do prefer ATI overall for everything else other than FSX.

For the UK I use Horizons VFR GenX Photo Scenery, UK2000 VFR airfields vol 1&2 and many Xtreme airports too along with the recently released Treescapes from Earth simulations which includes about 113,000 tree autogen files for England and Wales, which amounts to millions of trees I'm sure. Treescapes makes a huge difference to the immersion factor and is definately worth buying if you spend alot of your time flying over UK photo scenery.

Oh by the way Simon UK2000's rendition of Heathrow is far far better on frame rates than Aerosofts edition is, it is also kept up to date more often too, I think there is a new update coming out from UK2000 pretty soon.

For Europe and the rest of the UK I use GEX Europe and this does make a vast improvement to performance as each texture tile area has a balanced amount of autogen on it, and this helps massively to keep frame rates very stable, I rarely see more than about 8% variation in the instant average frame rate as reported by the MSFS frame rate counter if you enable that average facility in the counter, although this can also be largely influenced by the quality of the aircraft gauges in use and their code optimisation.

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Thanks for this report. every i7 owner I know is a happy camper with FSX performance wise. Compared to Core 2 Duo as example, the per clock single core effictive throughput has gone up very much, you see that when a full "Create schedules, files and traffic" goes down from 3.5 hours to a bit over one hour even with lower nominal clock rate.

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  • 1 month later...

Hello Simon:

Thanks for this post! It seems as if we have virtually identical systems, including the monitor. I'll be trying out all the settings you listed, as MTX didn't quite work out for me in the 1st install due to some consistent FPS hits.

I do have a few questions for you, though, if I may:

1. What external FPS Limiter do you use? I'd like to try out the FSX "unlimited" FPS setting with the limiter.

2. Re the [bufferpools] tweak, I've also tried the "Usepools = 0" setting, with identical results. Question: does the "RejectThreshold" entry look like this in the FSX.config:



3. You mention deleting some on-ground aircraft via "STB." What is "STB?"

Finally, I wonder whether you'd be kind enough to send me a copy of your FSX.cfg file, since we do have the exact same system? I'd like to try it out first. My e-mail is:




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When using the external FPS limiter you are supposed to set the internal limiter to unlimited. It works 1000% better than relying on the FSX FPS limiter, it is far smoother and consistent, even when playing replays for example.

Details about the external limiter can be found here http://www.simforums.com/forums/forum_posts.asp?TID=29685

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It does work though because the frame rate is still limited but by an external dll rather than an internal one. I can get over 80 frames a second most of the time without the limiter, but with the external one I limit it to 30FPS and it very rarely drops below this. I see no odd behaviour at all in FSX and I do know what I'm looking for.

Try it, it wont do any harm at all, all you are doing is launching FSX with a batch file.

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Hello Simon:

I do have a few questions for you, though, if I may:

1. What external FPS Limiter do you use? I'd like to try out the FSX "unlimited" FPS setting with the limiter.

2. Re the [bufferpools] tweak, I've also tried the "Usepools = 0" setting, with identical results. Question: does the "RejectThreshold" entry look like this in the FSX.config:



3. You mention deleting some on-ground aircraft via "STB." What is "STB?

I think you got the answers to 1 and 3 already. Concerning 2, that is how the entry should look. However, if you have UsePools=0 that will take precedence and the RejectThreshold does not get used.

Very recently I have started using UsePools=0 again, because I am not having the stability issues with it that I did before. Yes there are occasional autogen flashes but I can live with those, special effects and scenery objects in the sky but they always work themselves out in the end. Bottom line is this is just another choice to make along with the many other sliders that are available in FSX, and has it's pros and cons.


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