May BYTE magazine article out today featuring java tools, including java chips:
Java Chips: The Hardware Solution
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May 1998 / Cover Story / How To Soup Up Java / Java Chips: The Hardware
Solution
The Java virtual machine (JVM) isn't virtual anymore -- it's real. New
Java chips can execute Java bytecode as their native machine language,
making it unnecessary to interpret or compile the bytecode into some
other CPU's machine language.
In theory, this could allow Java to run as fast as native code on other
CPUs -- if Java chips were as powerful as other CPUs. In practice, most
Java chips will be sub-$50 processors, because they're designed for
network computers (NCs), TV set-top boxes, smartcards, and other
embedded devices. Only one company, Sun Microelectronics, is known to be
developing a high-end Java processor (ultraJava).
Nine companies are working on Java chips: Sun, NEC, IBM, Fujitsu, LG
Semicon, Rockwell, Siemens, Patriot Scientific, and International Meta
Systems (IMS). Seven of them (Sun, NEC, IBM, Fujitsu, LG Semicon,
Rockwell, and Siemens) are designing their chips around Sun's picoJava
core, which is available for licensing. Patriot modified an existing
processor to run Java, and IMS is working on an independent design.
Sun plans to ship its first Java chip, the microJava 701, in the second
half of this year. Later, Sun plans to introduce additional 700-series
microJava chips, plus some lower-end 500-series and 300-series chips.
For the high end, Sun is designing the ultraJava for 1999 or later. It's
for graphics workstations and will compete against high-end CPUs of
other architectures, says Harlan McGhan, technical marketing manager.
So far, nobody has shipped actual products with Java chips. Sun has
announced the JavaBlaster, a $99 ISA card that turns old PCs into
Java-based computers, but it won't appear until after the microJava 701
ships. Siemens is designing a picoJava-based smartcard. Rockwell might
use its JEM1 chip in navigation and communications systems. Patriot has
shipped more than two dozen development kits for its PSC1000.
Java chips aren't limited to running software written in Java, any more
than other CPUs are. Programmers can use any high-level language that
has a bytecode compiler. In fact, Sun is introducing C/C++ compilers
that generate bytecode. The picoJava architecture defines about half a
dozen extended bytecode instructions to support C/C++ and low-level
hardware functions, such as memory writes, on-board cache control,
access to control registers, and power-up/power-down diagnostics.
Is this heresy? No, says Sun. Java chips must support those functions so
developers can write OSes, device drivers, and other low-level programs.
Regular Java can't do it because Java source compilers don't generate
the extended bytecodes. Even if they did, the bytecode verifiers built
into JVMs would reject the extended bytecodes as illegal. This preserves
the safety of Java applications while permitting developers to write
low-level system software for Java chips.
Patriot was the first company to demonstrate a working Java chip
(November 1997). Instead of licensing Sun's picoJava core, Patriot took
an existing Forth chip and reprogrammed the microcode to recognize
bytecodes. The PSC1000 already had a stack architecture, because Forth,
like Java, is a stack-oriented language. Patriot's PSC1000 costs less
than $10 in volume.
Marc Tremblay, a chip architect at Sun, predicts that low-end Java chips
based on the picoJava core will run Java about 20 times faster than
interpreters running on a Pentium at the same clock frequency. Tremblay
thinks the chips will deliver about five times as much performance as a
just-in-time (JIT) compiler running on a Pentium.
Is that fast enough? By the time the chips come out, the best JIT
compilers might deliver more performance on fast CPUs than low-end Java
chips. However, that won't threaten the two most important markets for
the chips: inexpensive devices that can't afford a Pentium-class CPU but
still need to run Java at acceptable speeds and low-memory devices that
lack the resources for a full-size JVM and a JIT compiler. |
