Using multiprocessing in AutoCAD

All Autodesk's CAD products based on AutoCAD 2000i, 2002, 2004, 2005, 2006, 2007, 2008, 2009 and higher are multi-threaded, display operations run on multiple processors.

The WHIPTHREAD variable controls the way how AutoCAD uses the second processor (or core) for display operations.

• 0 - use only a single processor (as A2000)
• 1 - regen done on multiple CPUs
• 2 - redraw done on multiple CPUs
• 3 - both regens and redraws done on multiple CPUs
  

Multi-CPU and multithreading systems are used by AutoCAD also for other operations, e.g. for the mental ray rendering (2007 and higher), background publishing, xref loading, or for background loading of .NET Framework.

Intel processors with the hyperthreading (HT) and dual-core technology are considered by the operating system as multiprocessor PCs.