The Performance Monitor for AutoCAD can alert you as to when virtual memory is running low so you can save any work in progress before the system potentially decreases in stability. Such a condition is less likely to happen on a 64-bit versus 32-bit environment. The Performance Monitor for AutoCAD runs on Microsoft Windows 7 or Microsoft Windows Vista. Developed as a Microsoft gadget, it is not compatible with Windows XP.
The Performance Monitor for AutoCAD team, and in particular Senior Product Designer,Sara Makarenko, have authored a white paper on this topic:
Getting under the hood is alive in the lab.