Sun switches course with new Java chip
MicroJava 701 based on new core: Will execute both Java and legacy code
This picoJava II core will power Sun's first Java chip, the microJava 701, which will be unveiled today in San Jose, CA at Microprocessor Forum. Industry observers expect the microJava 701 to power products like Sun's JavaStation line of Network Computers.
PicoJava II will have a six stage pipeline (picoJava I's is four stage) and a new core in which many more sequences of instructions can be folded and executed in a single clock cycle. And "many of those sequences," says Harlan McGhan, picoJava's technical marketing manager, "are sequences that you commonly see in a C program." This means that picoJava II processors will be used to execute Java as well as legacy code, according to McGhan.
PicoJava II is not a chip. It is intellectual property -- the core design that chips like the microJava 701 and its higher-performance sister, the ultraJava (expected in late 1998), will have at their core.
McGhan says that when picoJava was first designed, his team expected most of the Java operating system code to be written in Java, but when it came time to design the microJava 701, "it became clear to us that at least parts of the Operating System were not going to move to Java anytime soon." McGhan says that, as things now stand, the OS is about 60% Java.
McGahn's colleague, V.R. Ranganath, who is the group manager for microJava, adds that "even if JavaOS becomes 100% pure Java, none of the RTOSs (real time operating systems) will be rewritten in Java, at least in the near future. The embedded marketplace, he says, really needed something that will "run C under the hood."
Sun claims that the microJava 701 will offer the industry's best Java performance for the price as well as C and C++ performance "comparable" to other similarly-priced products.
Jim Turley, a senior editor with the Microprocessor Report newsletter, says that while picoJava I licensees like Mitsubishi, NEC, and Samsung are expected to ship products based on the earlier core, these licensees "look like they're left holding last year's model." Turley is also skeptical about the performance increases that the various Java chips are supposed to bring. Referring to Sun, he says, "They've been extremely coy about discussing performance," adding that "picoJava I has been out for a year and Sun has refused to give any performance numbers."
McGhan counters that Sun will announce "an industry leading CaffeineMark" at today's Microprocessor Forum show.
One licensee that will not be implementing the picoJava I core anytime soon is Rockwell. Just last month they beat Sun to market with the first microprocessor to directly execute the Java instruction set -- the JEM 1. Sources at Rockwell say the JEM 1 is based on the Amp line of microprocessors that Rockwell has been developing since 1982 and has nothing to do with picoJava. They add that the company has no immediate plans to do anything with picoJava.
McGhan says that the real advantage of the 701 is that it will run Java bytecode at an optimized level from the start. On other microprocessors, where Java is interpreted, he says, just in time (JIT) compilers are able to perform their optimizations after several passes of the Java code. Because the 701 executes Java byte-code directly "there will be a substantial increase on the first pass compiler number," McGhan claims, adding, "probably a factor of two or three." And because they use no JIT, systems based on the 701 chip will require less memory to execute Java with reasonable performance. Industry observers say that Sun's upcoming Hot Spot JIT acceleration technology, for example, will require from 16 to 32 megabytes of memory - not exactly what you'd expect for a JavaStation.
At 200 MHz, the microJava 701's frequency will be 50% greater than the 133 MHz expected from picoJava I-based chips. It will be based on a .25 micron CMOS process, and come with 2.8 million transistors, a 33 MHz PCI bus, and a 66 MHz memory bus. With power dissipation expected at about 4 watts it will not be a likely candidate for the hand-held market. The 701 will sample in spring of 1998 and is expected to ship in volume by the end of 1998.
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