Although the Gen 8.x Build Tool, Diagram Trace Utility & Gen Studio are all Java based, only the Build Tool is a pure Java application. Therefore, only a 32-bit JRE can be used for the GEN85JRE & GEN80JRE environment variables.
Only the Build Tool is a pure Java application that is invoked via a direct launch of a java class.
The Diagram Trace Utility & Gen Studio are 32-bit Eclipse executables so a 32-bit version of the JRE is required otherwise they will fail to load the %GEN85JRE%\bin\server\jvm.dll file Error message dialogs will either be:
"JVM Terminated Exit Code = -1" followed by the JVM options
"Failed to load the JNI shared library "%GEN85JRE%\bin\server\jvm.dll""