The Sunnyvale, Calif., campus of Sun Microsystems Inc. is a quiet and peaceful place with six low-rise buildings connected by tree-lined walkways. But the tranquility masks a frightening reality—Sun is in serious economic trouble. The company was badly splattered by the burst of the dot-com bubble of 2000. Revenues for this once towering colossus of the server industry went south, and its stock plunged from more than US $60 in 2000 to less than $3 in 2002. Recently, the stock has been slowly but steadily climbing, and at press time it was selling at more than $5—a sign that the worst may be over for the company.
But Sun, headquartered in Santa Clara, Calif., is still far from its glory days of the last decade. It could use a small miracle to get back solidly on its feet, and at last the company may have one: a new microprocessor chip intended for the volume servers that are the heart of data centers running the information and Web processing for businesses, universities, hospitals, factories, and the like. Sun's engineers have had working chips since last spring and are now heavily into testing and debugging them and making design changes for the next fabrication run in early 2005.
The server business generates $50 billion a year, according to Jessica Yang, a research analyst at IDC, Framingham, Mass., and Sun's share recently is about 12 percent—down from 17 percent just four years ago.
Sun's new chip, called Niagara for the torrent of data and instructions that flow between the chip and its memory, was designed from the ground up to do away with the impact of latency—the idle time a microprocessor spends waiting for data or instructions to arrive from memory. This latency is one of the biggest impediments to the microprocessor's ability to do real work.
Niagara was not conceived at Sun. It started life in classic Silicon Valley fashion, as the brainchild of a Sunnyvale start-up called Afara Websystems Inc. "'Afara' means 'bridge' in the west African language Yoruba," explains Stanford University professor Kunle Olukotun, one of the company's founders [see photo, " "]. Completing the founding trio are Les Kohn, a microprocessor guru who has designed microprocessors for both Sun and Intel Corp., and industry insider Fermi Wang. The company did not plan to sell microprocessors but instead to sell complete servers built around its approach to microprocessor design.
When funding all but vanished after the terrorist attacks of 9/11 and the recession that began in 2001, Afara began negotiations with Sun, and in 2002, the server giant acquired the start-up.
Niagara diverges from other microprocessors in the way it processes instructions—the individual commands that come from software applications like databases and spreadsheets. These applications enter the microprocessor as a stream of instructions, which the microprocessor executes. The instructions tell the microprocessor what data to operate on, what operation to perform on them, and what to do with the result. The instructions travel through a series of circuits called a pipeline, which resembles an automobile assembly line.
Each stage of the pipeline performs one step of the instruction execution every clock cycle. In the first stage of the Niagara design, the pipeline gets an instruction from memory, an add instruction, for example. The second stage selects that instruction for execution. The third stage determines what kind of instruction it is—in this case, an add instruction. The fourth stage executes the instruction. The fifth stage is used for getting data from memory. add instructions, however, do not access memory, but get their data from registers. So the instruction passes through the memory stage and on to the final stage, during which the pipeline writes the results of the operation back into a register.
Every clock cycle, a new instruction enters the pipeline. If all goes well, the instructions march through the pipeline in lock step, and one instruction is completed with each tick of the microprocessor's clock. So a six-stage pipeline can have six instructions at different stages of execution at one time.
The rate at which a microprocessor executes instructions is the most important measure of its performance. It is simply the product of its clock frequency and the number of instructions it executes in each clock cycle. Ever since the first microprocessor was invented in the early 1970s, architects have been on a relentless scramble to improve performance.
Typically, the designers have pursued their goal on two fronts: increasing the clock frequency and increasing the number of instructions the processor can execute in one clock cycle. Thanks largely to the semiconductor industry's ability to produce ever smaller transistors, clock frequencies have soared over the past 30-plus years by five orders of magnitude—from tens of kilohertz to more than 4 gigahertz.
To increase the number of instructions per clock cycle, architects have added more pipelines. Some microprocessors today, such as Intel's Pentium 4, have eight pipelines, allowing these chips, in principle, to complete eight instructions in parallel during a single clock cycle.