Just released version 1.2 of my PowerCoreTools CPU managment script for 3ds Max
A tool to control CPU usage while 3ds Max is rendering. Automatically sets process priority and affinity ( the number of CPU cores the render process uses) at render start. Restores the initial settings when the rendering is done. Can be configured to run in a complete transparent No-UI mode, which is launched right after 3ds Max has started.
This keeps your workstation responsive for other tasks while rendering. A second 3ds Max session stays responsive and can be used to continue work on different tasks.
A look at the following screenshot will probably tell more than thousand words: