Culled from the pages of AVSIM and other online resources, here are a few Essential FSX Tweaks which may make your FSX experience that much more enjoyable
Autogen Tree Tweak
Created by Matt Fox, the linked files will adjust how autogen trees are drawn in the simulator. Rather than using a great number of tree types and sizes, Matt's file limits the species and sizes, thus giving the computer a lot less work. In the short time FSX has been available (pre-retail) via Best Buy and others, this tweak has become the de-facto "Must See!" due to it's impressive performance improvements. This is done at the expense of autogen diversity, but it would appear that autogen *density* remains at FSX-advertised levels. Be sure to check the forum discussion link for any more files or ideas replacing these, as they may go out of date...
Original File (10/7/2006)
Tweaked File (10/8/2006)
Original Thread (README!)
Autogen Texture Adjustments
Autogen textures are apparently made from DXT5 textures, which impose a bit of penalty as compared to other DXT styles. A few friends over at FS2004.com started playing with the texture compression of the autogen and found some performance gains.
Discussions on what it is and how to do it... (READMEs!)
Cloud Texture Adjustments
As with FS2004, FSX uses aggressively sized textures for clouds in order to bring you a vivid flying experience. Unfortunately, the textures may be a little too big for some systems.
Right now, only one person has taken to resizing the cloud textures and providing them to the public. Although the modification and distribution of original FSX textures is most likely a violation of the EULA, here is the link to the thread this method is being discussed in...
Linky and (README!)
Others have discussed importing FS9-based ActiveSky texture files into the FSX world, and have noted appreciable performance improvements with minimal visual problems (*if not visual improvements for those who prefer the 3rd party clouds) with them as well. You would need to have some knowledge of moving files and backing things up before attempting this, but it's out there.
Autogen Building Roof Tweak
Also created by Matt Fox, the linked file will adjust how autogen roofs are drawn in the simulator. The file reduces the number of roof types used on buildings, which may lead to performance improvements in the same way Matt's trees adjustment did. Not much commentary on this tweak, as most feel that its the trees causing the autogen performance penalty.
Original Thread (README!)