If you have a 64-bit JVM, it will fully utilize the 64-bit hardware. There is no need to specify any options to do that. The -server and -client options distinguish between two JVMs that behave slightly differently when it comes to compiling bytecode to native code, some slight differences in heap management, and a few other differences. But they both make use of the 64-bit hardware. You do not need the -d64 option to run in 64-bit mode. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4204541#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...