Intel hyperthreading shows Digital roots

Although Digital often floundered when trying to sell its own chips, the defunct computing giant left behind technologies and engineers that are at the core of many recent and coming advances.

"There is all this cool technology coming out on PCs that came from Digital," said Dean McCarron, principal analyst at Mercury Research. Nonetheless, McCarron, among others, noted that these breakthroughs rarely helped Digital's bottom line.

Digital was acquired by Compaq Computer in 1998, and its remnants became part of Hewlett-Packard earlier this year when HP completed its acquisition of Compaq.

Nonetheless, technologies with Digital genes march on, including HyperTransport, a high-speed method of chip interconnection championed by Advanced Micro Devices; a future version of Intel's Itanium family of processors; and low-power chips for cell phones and handhelds from both those companies.

Intel's hyperthreading, which involves breaking up an application for easier digestion by a computer's processors, derives in part from work on simultaneous multithreading performed by a team of researchers at the University of Washington and Digital, an Intel representative confirmed. In 1997, Intel licensed the patents and hired many of the employees who worked on the project as part of a massive legal settlement between the companies.

The threading work will likely leave a lasting impact, as it remains one of the areas of chip architecture where substantial performance gains can likely be achieved without major penalties. With hyperthreading, a chip can run two parts of an application at once, boosting performance by up to 30 percent. The gains come because the application can take advantage of different parts of the chip at the same time.

"We're at the place where we have lots of idle resources we can use," said Dean Tullsen, an associate professor at the University of California, San Diego, and one of the Washington researchers who published the papers on multithreading in 1995, attracting Digital's attention.

In the future, "helper threads" that run ahead of the main application to clear the computing path will likely appear, Tullsen added.

The Digital divide
The transformation of Digital into a posthumous chip powerhouse lies in the circumstances of history. Founded in 1957 by Ken Olsen, the company gained prominence in the minicomputer era and emerged as a chief rival to IBM. The PDP-11, a minicomputer released in the '70s, still garners fans to this day.

In the '80s though, the company missed both PCs and Unix because of its obsessive focus on minicomputers. Olsen didn't believe a big market existed for these lower-end products. "He was famous for saying, 'Unix was about as interesting as a Russian truck,'" recalled Nathan Brookwood, an analyst at Insight 64 and a former Digital employee.

In the '90s, the company played catch-up in both markets, but was often saddled by delays and faced the problem of trying to dislodge established leaders. The company developed the Alpha chip in 1992. While touted for its performance, the chip and servers containing it never achieved the same sort of widespread acceptance in the marketplace as competing products from Sun Microsystems, HP or IBM.

"A lot of the research stuff--the sales guys couldn't sell (it) because it was ahead of its time," said Richard Belgard, a patent consultant and former engineer at competitor Data General. "Alpha was great technology, but who the hell needs another microprocessor?"

Digital also built a state-of-the-art chip fabrication facility in Hudson, Mass., that manufactured Alpha chips and StrongArms, an energy efficient chip for cell phones. That plant rarely, if ever, ran at full capacity.

Toward the end of the decade, the intellectual exodus began. In May 1997, the company filed a lawsuit alleging that Intel's then-future Itanium chip violated 10 Alpha patents.

Despite the public rancor, the two companies settled the suit by October. Intel obtained the Hudson fab and the rights to make StrongArm, while Digital got $700 million. The two also entered into a 10-year cross-licensing arrangement.

Simultaneously, Intel hired a number of the Digital engineers and gradually began to incorporate the company's technology into its own product lines. The StrongArm became the foundation of Intel's IXA network processor line for telecommunications equipment. The XScale chip, used in the latest Power PC handhelds and Sony's Clie, derived from StrongArm as well.

A deal between Compaq and Intel in June 2001 led to a further brain transfer. Engineers acquired from Compaq in that deal are now working on compilers for Itanium and future versions of the chip, including "Chivano." HP still sells Alpha servers but plans to phase them out by 2004.

Some, though, ended up somewhere other than Intel. Dirk Meyer, one of the chief Alpha engineers, went to AMD in 1996 and co-managed the development of the Athlon, the successful desktop chip released in 1999. Among other Alpha bits, the Athlon uses a bus originally developed for Alpha.

Hammer, the next big chip from AMD, also derives design principles from Alpha, said Brookwood, and many Alpha alumni work on the chip. One of the performance enhancements is an integrated memory controller, an idea touted years earlier on Alpha. In true Digital style, the Alpha chips that were to feature multithreading and integrated controllers have been delayed several times.

HyperTransport, which will connect Hammer chips, came from work between AMD and Alpha Processor, a defunct joint venture between Compaq and Samsung. Thirty-five engineers from API form the bulk of AMD's Boston Design Center

Similarly, Rich Witek and Greg Hoeppner, two former Digital engineers who left the company after the Intel settlement, subsequently formed Alchemy Semiconductor. In February 2002, AMD acquired Alchemy and made it the center of its handheld strategy.

While many of these underlying ideas came from Digital, the work to embody them in actual products has been performed by the companies touting them. Inserting hyperthreading into the Pentium 4, for instance, was an in-house job for Intel.

"Some of the actual concepts were developed there, but the implementation was done by Intel," the Intel representative said.