Flight Simulator X: Performance tweaks

Flight Simulator X has not even been officially released in the USA, and we already have a handful of people complaining about its performance. It's become pretty much clear that you need recent hardware to run FSX decently, but even people with high-end systems are having trouble finding optimal settings for it. The major performance hit comes with the new autogen trees and buildings, which can completely ruin your flight experience over big cities if not configured properly. This guide's objective is to provide some tweaks for you to optimize the simulator performance.

Some tweaks presented in this guide will require modification of the FSX configuration file. Please have a backup copy of that file before applying any modifications!

Note: To view the configuration file (FSX.cfg), type "%appdata%/Microsoft/FSX" (without quotes) on Windows Explorer. You can open it with Notepad.

1. Post-installation tweaks

After you install such a big software (over 13GB), it is highly recommended that you defragment and reboot your system. The installation have probably spread FSX files everywhere on your hard drive, thus causing a longer response time when you try to access those files. The disk defragmentation will put the files in a specific sector of the hard drive for faster access.

Next thing I want you to check is if the video card drivers are updated and configured properly. Leave all settings at "Application Controlled" on the driver and configure the display settings only on FSX... this might give you a few extra FPS depending on your video card. (Thanks LEOGETZ @ Aerovirtual)

With the disk defragged and the video card configured, you are ready to start FSX. Try to find the optimal settings for your system by increasing or reducing the texture quality / autogen density. This might take some time, but I recommend that you only proceed with tweaking after finding your optimal settings.

2. Getting rid of the blurries

Tweak by "Torgo 3000 " - Original Post

There are several ways to adjust how much CPU time FS devotes to loading scenery and textures. The easiest way is to set the target frame rate slider to a value that your machine can consistently achieve. The lower you set the slider, the more CPU time is diverted from rendering to loading data. Another thing you can do is to modify the following variable in FSX.CFG:


FIBER_FRAME_TIME_FRACTION=0.33

This variable determines the amount of CPU time given to loading scenery data as a fraction of the time spent rendering. For example, the default value of 0.33 means that for every 3 milliseconds spent rendering, FS will give 1 millisecond to the scenery loader. If necessary, you can use a larger value to devote more time to loading. Or, if you don't have a problem with the blurries and you want slightly higher frame rates, then you can use a smaller value. Again, this variable is only available in the final release version of FSX and is not available in the beta or demo.

3. Changing the bandwidth helps prevent stutters

This is a tweak that used to work in FS2004, and is again working in FSX. To help prevent stutters, change the following line in your FSX.cfg to a higher value. Most people are happy with a bandwidth of "400".

[DISPLAY]
TEXTURE_BANDWIDTH_MULT=40

4. Better autogen performance

Tweak by Matt Fox - Original Post

Editor Note: This tweak is definitely worth a try. Great performance improvement and still great autogen quality!

First backup AutogenDescriptions.spb located in your FSX\Autogen folder. Then unzip the file attached to this post in it's place.

What this does is dumb down your autogen trees so there are a lot fewer types of trees displayed. This is an extreme version meant as a proof of concept that basically sets one tree for each different tree category, whereas FSX default may have 10 or 20 different trees for each category. If it helps, I'm sure someone with more free time than me could come up with several different customized versions, each with a different level of complexity. It's pretty easy to adjust with the SDK.

I don't think this affects the total number of trees displayed. Just the number of different types and variations.

5. Replacement files for better performance

There are quite a few replacement files for FSX textures now. They will increase performance by reducing the textures resolution.

5.1 - Replacement autogen tree textures

Tweak by Mike Kelly - Original Post

The textures have been reduced from the originals and the DXT1 format and alpha channels have been preserved. The dimensions have been reduced by 50%. This results in a reduction in total size of the textures from 10.7MB to 3.9MB. All seasons are included. Download the replacement textures.

5.2 - Replacement cloud textures

Tweak by Mike Kelly - Original Post

The textures have been reduced from the originals and the alpha channels have been preserved. The dimensions have been reduced by 50%. This results in a reduction of the total size of the textures from 39.8MB to 15.3MB.

There were no adverse visual effects that I could see although the reduced clouds do seem slightly more "fuzzy". IMHO this is not bad, just different. Download the replacement textures.

5. Autogen tweak that might help

Tweak by "PC-12C Pilot" - Original Post

Editor Note: This tweak haven't done much for me, but it's said to do miracles on some systems. Worth a try!

Many of you have been frustrated that you can't control the density of autogen trees verses buildings because we only have one slider to cover both of them. Some have also been frustrated that our lowest autogen setting is more dense than FS2004 at max density.

If you add these two lines to the [TERRAIN] section of your FSX.CFG, you can define the max number of objects in a terrain cell for trees and buildings independently. The slider will scale down from the numbers you set as the slider is moved to the left. The max tree value in FSX as released is coded to default to 4500 and the building default is 3000 (as shown below) and the absolute max FSX will recognize at all is 6000. Of course if you raise the values beyond the defaults, you will obviously be increasing density and lowering fps (so don't complain if you do this...). The point in sharing this information is that with these settings you can specify what the values are yourself. Be sure not to set either number to 0 as that will cause problems, but setting it to a very lower number will give you nearly 0 objects.

TERRAIN_MAX_AUTOGEN_TREES_PER_CELL=4500

TERRAIN_MAX_AUTOGEN_BUILDINGS_PER_CELL=3000