waves.com and download the upgrade to 3.2. Waves has">

Pro Audio Support

Q:
Why does my Renaissance Reverb take so much CPU power on my Windows system?
 
A:
If you have version 3.0, you should go to waves.com and download the upgrade to 3.2. Waves has reduced the CPU consumption by 30-40%, though this is still a very CPU-heavy plugin.

Download version 3.2, uninstall 3.0, and if given the option of Auto or Custom, choose Custom, and Select All and Next until finished. Install 3.2, and go to your c:\program files\waves directory and delete c4.dll.