I was trying to install both x86_64 and i386 versions of java-1.5.0-ibm but there is packaging problem with conflicting files (message from yum): Transaction Check Error: file /var/www/cgi-bin/java-rmi-1.5.0.5.cgi from install of java-1.5.0-ibm-devel-1.5.0.5-1jpp.0.1.el5 conflicts with file from package java-1.5.0-ibm-devel-1.5.0.5-1jpp.0.1.el5
32 and 64 bit IBM JDKs can now be installed in parallel.