PALO ALTO, Calif. -- Sun Microsystems Inc. has taped out the picoJava core that will form the heart of its first Java-specific microprocessor, a source at the company said. The CPU incorporates a hardware-based Java Virtual Machine (JVM) that's said to deliver a tenfold performance increase over a software-only JVM implementation.

PicoJava still must be fitted with the input/output and memory-access capabilities that will turn the core into a fully integrated chip. But the Sun source expects the processor to be ready for release early next year. (The chips themselves will not be marketed by Sun, but by picoJava-core licensees LG Semicon, Rockwell Semiconductor Systems and NEC.)

The status of Sun's planned trio of Java chips--dubbed picoJava, microJava and UltraJava--has been the subject of intense interest ever since the processors were first discussed by Sun a year ago. Little news has emerged since that time, though company officials said that the efforts remain on track.

The technical details of the chips have been the subject of even greater speculation, especially in light of the performance questions that have swirled around Java in recent months.

In picoJava, which is aimed at the embedded market, Sun is addressing performance via the inclusion of a hardware JVM that enables Java bytecodes to be executed directly by the chip without passing through an interpreter. "The hardware JVM delivers performance comparable to a just-in-time compiler and in some cases is faster," said a Sun source who requested anonymity. "Let's say you're trying to invoke a method in Java. That would take a few hundred instructions in a software interpreter. But in the hardware JVM, it would result in roughly 10 to 20 microinstructions."

To facilitate embedded applications, picoJava is also being outfitted with extra instructions--called extended bytecodes--not found in the standard Java instruction set.

These extended bytecodes correlate directly to low-level chip-control operations such as register accesses, cache control and load and store operations.

In practical usage, the extended bytecodes are supposed to make it easier to control modems and network-interface devices. To speed performance, the extended bytecodes can be executed directly by picoJava in the same way it handles the standard Java instructions.

The hardware JVM and the extended bytecodes will also be included in microJava, which is positioned as a CPU for network computers.

Hybrid approach
However, a different architectural tack is being taken with UltraJava, the high-end processor intended to power workstations. According to the Sun source, UltraJava will utilize a hybrid approach that incorporates both the hardware-JVM technology as well as characteristics of a conventional RISC processor.

Sun engineers are still working to nail down implementation specifics. Also, software executing on UltraJava will be augmented by Hot Spot, the optimization technology that Sun is developing. But it's unclear whether Hot Spot will be used as a software adjunct or incorporated directly into the processor's JVM.

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