CACAO is a research Java Virtual Machine developed at Vienna University of Technology. It compiles the class binaries while running (no interpreter), resulting in faster execution. It is an academic project and was originally driven by some students doing practical training or diploma theses on specific topics.
The first version of CACAO was released at 1997 as a faster replacement of Sun's implementation, which at that time only had an interpreter. The recent Sun's virtual machines also use just-in-time compiling.
CACAO gained much more activity after becoming a free software project in 2004, distributed under the term of the GNU General Public License. It uses GNU Classpath as its class library.
CACAO supports Alpha, ARM, MIPS (32 and 64-bit), PowerPC (32 and 64-bit), S390, SPARC64, x86 and x86-64 architectures.