While discussing the implementation of the graphical paging feature with some people over at the C2C forum they made me aware of a tool that can increase the amount of available memory for 32bit executables on 64bit machines from 2 GB to (almost) 4 GB.
Some background: Civ4 is implemented as a 32 bit application which limits the amount of available RAM to 2 GB, even though 64 bit machines can provide much more than that (which your computer is likely to have).
So if you have a 64bit operating system, you can download this tool and execute it on the Civ4BeyondSword.exe file in your BeyondTheSword folder to increase the available memory to 4 GB (this applies to all BtS games and mods).
Copy and rename your .exe-file first!
If you are running a 32bit OS, this tool unfortunately cannot help you.
I really recommend doing this if you have problems with performance.