The information in this article applies to: 

• SONAR 8.5
• SONAR 8
• SONAR 7
• SONAR 6
• SONAR 5
• SONAR 4
• SONAR Home Studio (All Versions)

The audio configuration dialog (Options-Audio) has a Checkbox "Enable Multiprocessing Engine" on the Advanced Page. 

This Checkbox is  only active  on multi-processing (or hyper-thread) machines. When checked, the audio engine will use a dedicated worker thread for each CPU, and optimally distribute mixing and DSP tasks across multiple CPU's. You will notice significant performance benefits on true Multi-processor systems with this option enabled.