Conservative Memory Usage:

Gimp is optimized to speed i.e speed is more important than memory usage. Enabling Conservative Memory Usage will "optimize" Gimp to use less memory. The tradeoff is of course speed but if your system is low on memory then it can be an option to use Conservative Memory Usage.

Tile Cache Size:

This is the most important parameter that Gimp has, if you set it to low Gimp will be very slow. There isn't a upper level of how much memory that you can give Gimp i.e give Gimp as much as you can. But don't give Gimp more that your physical memory (i.e pure memory without swap). In reality you have to measure how much memory you usually use and give Gimp a little less than the rest of it.

Maximum Image Size:

Gimp will warn you if you try to create images bigger than this value.

Install Colormap:

Not used since we use GdkRgb now

Colormap Cycling:

Still TODO

Try to Write a Thumbnail File:

By default when you save a image a thumbnail file will be created storing a little image of your image. When you mark a image in the file open dialog you will see this thumbnail. If you set this option to Never you have to press on the thumbnail button in the file open dialog to be able to see a thumbnail of your image.

"File > Save" saves the image:

This is by default set to Always but if you e.g saves your image on a networked disk (nfs, smb etc.) then saves some times are slow and saving always isn't that necessary. Instead you will only save when the file is really changed.

Index