Here are a few things you can do to help speed up AutoCAD.
Type IMAGEQUALITY and set it to “Draft” for faster-loading images in AutoCAD. When plotting however, you might want to switch it back to “High”.
Type IMAGEHLT on the command line and set it to 0. This will make AutoCAD highlight only the raster image frame when selecting it, not the entire image.
Set GRIPOBJLIMIT to a really low number to reduce the number of grips displayed when selecting multiple objects.
The system variable ISAVEPERCENT is set to 50 by default. Increase this number (100 max) to force AutoCAD to do full saves less frequently. If it is set to 0, AutoCAD will do a full save every time. The benefit of a full save is that it eliminates the wasted space in a drawing file – but it is slower.
Type VTOPTIONS on the command line to change how AutoCAD handles animated view transitions. It is a good idea to turn off the animated view transitions when dealing with large drawings.
Jimmy from JTB World posted a great suggestion for working with drawings that contain a XREFs, XCLIPs, & viewports. He suggested setting the system variable INDEXCTL to 3 to speed things up when switching between drawings.
If you have any tips for speeding up AutoCAD share them here as comments.