A Java processor is the implementation of the
Java virtual machine (JVM) in hardware. In other words, the
Java bytecode
In computing, Java bytecode is the bytecode-structured instruction set of the Java virtual machine (JVM), a virtual machine that enables a computer to run programs written in the Java programming language and several other programming langua ...
that makes up the instruction set of the abstract machine becomes the instruction set of a concrete machine. These were the most popular form of a
high-level language computer architecture
A high-level language computer architecture (HLLCA) is a computer architecture designed to be targeted by a specific high-level programming language (HLL), rather than the architecture being dictated by hardware considerations. It is accordingly al ...
, and were "an attractive choice for building embedded and real-time systems that are programmed in Java".
However, as of 2017, embedded Java is "pretty much dead" and no realtime Java chip vendors exist.
Implementations
There are several research Java processors tested on FPGA, including:
*
picoJava picoJava is a microprocessor specification dedicated to native code, native execution of Java bytecode without the need for an interpreter (computing), interpreter or just-in-time compilation. The aim is to speed bytecode execution up by up to 20 ti ...
was the first attempt to build a Java processor, by
Sun Microsystems. Its successor picoJava-II was freely available under the
Sun Community Source License
The Sun Community Source License (SCSL) is a community source software licensing model designed by Sun Microsystems that covers the J2SE and J2EE software development kits. Sun introduced the SCSL in 1998 to maintain compatibility within the Jav ...
,
[ and is still available from some archives.
* provides hardware support for object-oriented functions
*]Java Optimized Processor Java Optimized Processor (JOP)
is a Java processor, an implementation of Java virtual machine (JVM) in hardware.
JOP is free hardware under the GNU General Public Licenseversion 3
The intention of JOP is to provide a small hardware JVM for embed ...
for FPGAs. A PhD thesis i
available
and it has been used in several commercial applications.[ In 2019 it was extended to be energy aware (EAJOP).
Some commercial implementations included:
* The aJile processor was the most successful ASIC Java processor.][
*Cjip from Imsys Technologies. Available on boards and with wireless radios from AVIDwireless]["Imsys hedges bets on Java: rewritable-microcode chip has instruction sets for Java, Forth, C/C++"]
by Tom R. Halfhil]
* ARM9E, ARM926EJ-S is an ARM processor able to run Java bytecode, this technology being named ''Jazelle
Jazelle DBX (direct bytecode execution) is an extension that allows some ARM processors to execute Java bytecode in hardware as a third execution state alongside the existing ARM and Thumb modes. Jazelle functionality was specified in the ARMv5TE ...
''
References
{{Reflist
Java virtual machine
High-level language computer architecture