Is there a CPU that runs Java in microcode? [closed]

Closed. This question is off-topic. It is not currently ac开发者_JS百科cepting answers.

---

Want to improve this question? Update the question so it's on-topic for Stack Overflow.

Closed 9 years ago.

Improve this question

Java is a beautifully crafted OO language but the first thing I noticed is how slow it is (compared to C++). This is probably because it has to go through another layer of translation (the VM) instead of running directly in the CPU's native microcode.

My question: Do you know of any attempts to create Java-specific CPU's that run Java natively without requiring the software-implemented VM?

---

Sun designed the picoJava processor about 10 years ago, but it never went anywhere - there was no market for it at the time, and modern VMs render the concept pretty pointless.

Then there's the fledgling ARM Jazelle architecture.

---

The only reference I found so far to this conundrum is the following article:

http://www.theserverside.com/discussions/thread.tss?thread_id=59958

While I was initially interested in first knowing whether there are Java-CPU's and what they are, this thread sheds some light on why I haven't heard of any (until I read the learned replies here). The last comment, by Alex Besogonov, seems to be the best explanation:

Java bytecode is NOT suited to be run on real hardware. It's stack-based, so pipelining goes out of the window. In theory, one can do on-the-fly translation from stack-based to register-based machine, but it'll require A LOT of transistors.

So in reality, it's ALWAYS more effective to JIT-compile Java bytecode and then run it on a common CPU. There is one exception JVMs for low-power devices where the speed of hardware JVM is not a problem (remember Forth CPUs).

Of course, hardware can still provide few features to speed up JVMs. Like hardware-assisted forwarding pointers which allow to create fast real-time compacting pauseless GC (I assume Azul hardware has this support).

This is very interesting. Thank you all for your answers.

---

Azul Systems designs systems from the ground up with (massive services running on) Java in mind, including hardware-assisted garbage collection.

There's also GCJ for compiling Java to native code, though it is not a complete implementation of Java.

---

You might want to try JOP

It's open source and you can try it on your own hardware.