Keith is right, the support of multicores is available only in the RapidMiner Enterprise Edition (EE). Of course, you could run multiple instances of the community edition as Keith suggested. This will however neither increase the speed of any model building nor any evaluation process may be easily distributed among cores. The Enterprise Edition currently supports multicores in evaluation processes (cross-validation), paramater optimization and decision tree learning. In addition to that, the Enterprise Edition has several other advantages over the community edition including e.g. bugfix guarantees and automatic updates. Please have a look at the following website to obtain more information about the available packages:http://rapid-i.com/content/view/123/141/lang,en/
If you any more questions regarding the RM EE, just send us a mail.