Is there a way in rush to limit rendering to certain processors?
Yes, Rush version 102.42a9c (and up) provides an optional (and currently undocumented) ‘Affinity’ field in the rush/etc/hosts file. There’s a newsgroup article that covers its syntax and use. In 102.42a9c, this feature only works for Microsoft Windows. In a follow up release, it will support linux as well. Since OSX does not support processor affinity as of this writing (Nov 2010), affinity values for OSX machines will currently be ignored. When OSX adds support for this in the future, a future release of Rush will incorporate it as well. As of this writing, this Rush feature is not documented, save the above newsgroup article. This will change in the future once field testing can determine its proper usage.