Fallout 3 - Tips to Avoid Crashes

Fallout 3 - Tips to Avoid Crashes

This is one of our posts on tips to optimize your Fallout 3 experience -- giving you the best gameplay experience through a careful mix of cheats and mods. For the full index, click here.

Fallout 3, patched to 1.7, with just DLCs and NO mods, is actually very stable, all things considered. Most of the time, if you are getting a crash, removing all your mods will let you play through an area without a crash -- meaning mods are the problem.
Exactly why mods cause crashes is not easy to determine, but part of it probably has to do with computing load. The bigger the mod, the greater the chance of a crash, even if the mod is not buggy per se.

Game Freeze
This sort of crash happens when the game suddenly freezes up and you cannot access any controls at all. Typically you have to do a Control-Alt-Delete to access the Windows Task Manager and end the Fallout 3 application that way. It is rare, and often isolated to just a couple of locations. One location I have gotten this is inside the Recently Built Shack in Greyditch. It would suddenly occur, but not reliably in the same place.

This seems to be related to Fallout 3 using more than 2 CPUs. A workaround is to edit Fallout.INI: Open up the fallout.ini file in: My Documents\My Games\Fallout3
Find the line:
bUseThreadedAI=0
change it to:
bUseThreadedAI=1
Add another line after it and insert:
iNumHWThreads=2
This will limit the game to two cores and prevent the engine bug from causing the game to freeze. If the game still crashes write this iNumHWThreads=1

Mothership Zeta Operating Room Game Freeze
This is a slightly different type of Game Freeze, in that it is reliably repeatable. During the initial sequence where you are on the operating table and three aliens hover over you, the game may freeze. However, one alien in the back will continue to loop an animation where it seems to be mouthing something. During this time, you can still access the menu. Once that alien stops moving, the game will have frozen as usual, with no controls accessible.

This seems to be related to using the console command Purge Cell Buffers. Used at the appropriate time, this memory management command is said to help overall game stability, and there is a mod that does this periodically. In this particular instance, using Purge Cell Buffers causes the intro sequence to freeze.

This article on Fallout 3 Wiki has more comprehensive information and fixes for this and other potential game-stopping bugs.

Sudden Crash to Desktop
This sort of crash is generally caused by the game suddenly not having required information, which may in turn be related to an incomplete load of game information. Try a double-load: Load a game from the Main Menu, then load it again. This double-load gives Fallout 3 more time to load things in the background or work on things further than the area immediately around you. See Crash to Desktop on Save (below) for more information.

Sometimes a double-load won't help. A busy place with very far line of sight, such as Wilhelm's Wharf, can cause a CTD. I have consistently experienced it myself approaching Wilhem's Wharf from Greyditch, and with Mart's Mutant Mod loaded. Something you can try is to teleport yourself there. In the case of Wilhelm's Wharf, I used the console to get the Ref ID of Grandma Sparkle (by clicking on her when you have the console open), who is typically outside. Then I use player.moveto <Ref ID> to teleport my character to her location, which was previously inaccessible due to CTD on approach.
Using moveto typically causes the game to unload data, move you to the cell, and reload -- like a Fast Travel, only you aren't travelling that far. If you are indoors and using moveto to get to another location in the same indoor space, the game won't do that. It will just move you there since the entire indoor area is loaded. Outdoor cells are much smaller and using moveto can trick the game engine into clearing memory and reloading instead of trying to load more data and manage memory as you move forward in the game world.

Crash to Desktop (CTD) on Save
This sort of crash happens when you try to save the game: It immediately crashes you back to the desktop, even if you didn't move or do anything from where you last successfully save the game.
This is apparently related to trying to save the game when Fallout 3 has incompletely loaded data. Fallout 3 can sometimes have a lot of stuff to load and process. While the game may appear to work fine, the loading of information is actually not complete or properly done.

The workaround is to roll back to a previous successful save. Load this save from the Main Menu. Once loaded, look around you to force the game to load even more stuff and start processing the surrounding area. Now, load the same game again. Since a lot of information should now have been loaded and prepared, Fallout 3 doesn't have to start from scratch and has more of a chance to "catch up".

Changing this line in Fallout.INI also appears to help, by giving Fallout 3 more memory to work with:

iPreloadSizeLimit=26214400

The default is 25,600K (i.e., 26214400 bytes). If you have a lot of system memory, you can try changing it to 1 GB (1073741824) or even 2 GB (2147483648). If you are using hi-res textures or mods that introduce a lot of new textures because of new objects, this ought to help. As a precaution, double-load your games from the main menu, and make Clean Saves (saves that don't overwrite a previous save) every time.