SAN FRANCISCO — Alan MacPherson, a pioneering, larger-than-life patent lawyer in Silicon Valley, died suddenly of a heart attack on Dec. 8, at his home in Laguna Beach. He was 74.

The news came as a shock to partners at his San Jose-based firm, MacPherson Kwok Chen & Heid, where he was still very active as a patent litigator, prosecutor and counselor.

“Many people considered him to be the dean of patent law in the Bay Area,” said Edward Kwok, who founded the firm with MacPherson in 2002. “In this life he’s affected several generations of lawyers, and how he practiced law and those things that he taught us will stay with us.”

Standing well over 6 feet, MacPherson was a force of nature. Even at his advanced age, he would bike an hour from his home in Palo Alto to his law firm’s office in San Jose. (He split his time with the firm’s Irvine office.) In his mid-60s, he climbed Tanzania’s Mt. Kilimanjaro.

“He was one of those larger-than-life people,” said Fabio Marino, a former colleague, now a partner at Orrick, Herrington & Sutcliffe. “He just had a presence — very forceful, very energetic.”

Henry Bunsow, a veteran IP litigator with Howrey, called MacPherson a pioneer. “Alan MacPherson was at one time the best-known patent lawyer in Silicon Valley. I think he was one of the early patent practitioners to really take the business to another level.”

MacPherson started as a patent lawyer at Fairchild Semiconductor, and founded the IP practice at Skjerven Morrill MacPherson in 1980. Skjerven went on to become one of the leading patent boutiques in Silicon Valley, but collapsed following the dot-com bust in 2003.

One year before the firm folded, the Skjerven partnership voted to replace MacPherson as chairman, citing differences over the direction of the firm. MacPherson left six weeks later to start his own firm. The breakup was messy, with MacPherson filing a suit against his former partners.

“He was a genuinely nice guy and in most respects we had a very positive relationship — I think it was unfortunate it ended the way it did at Skjerven,” said Vernon Granneman, a former Skjerven lawyer who’s now at Pillsbury Winthrop Shaw Pittman.

MacPherson’s zest for his law practice was well-known. He would log more than 3,000 hours a year, even in his 60s. As late as this summer, he was trying a case for SiRF Technology before the pressure cooker International Trade Commission. Even as a senior partner he insisted on writing patent applications himself, a task usually reserved for associates.

The way he wrote patent applications was also remarkable to those who saw it. As a young associate, Tom Chen, a partner at MacPherson’s firm, went with MacPherson to interview an inventor. On the way back to the office, MacPherson dictated the entire patent application, complete with drawings, into a Dictaphone, while driving.

“As a young lawyer sitting there, I thought, ‘Well, that’s something I’ll be able to do someday,’” Chen said. “Now I realize this is something I could never do.”

MacPherson helped pioneer the so-called “clean room” defense when he was representing NEC in an IP fight with Intel in the early 1980s, said partner Kwok. Intel claimed that NEC had ripped off its programming in microprocessors, so-called microcode.

To fight the accusation, MacPherson gave an independent engineer the task of programming a chip to do the same thing as the NEC and Intel chips, but with no access to any previously written microcode — the clean room. The three sets of code were given to experts who determined that the similarities weren’t due to copying but due to the constraints of the task.

“After Intel lost, I heard about the law firm that created the clean room defense, so I had a lot of admiration for that and after I graduated law school I went there,” Kwok said.

Other clients over the years included AMD, Mosel Vitelic Corp. and Xilinx. MacPherson was known as a generous man, often taking time to help young associates along. Many of the lawyers at his firm trained under him at Skjerven.

MacPherson grew up in Maine and Vermont. He studied mechanical engineering as an undergraduate at Stanford and as a graduate student at MIT. He got his J.D. at Harvard Law School and worked at Bell Labs before moving to Fairchild.

MacPherson leaves his wife, Judy, six stepchildren and two children from his first marriage, Stuart and Sara. He remarried after his first wife, Suzanne, died in 1983.

A memorial will be held at Stanford University’s Memorial Church on Jan. 14 and is open to the public. The family requests that donations be made to Stanford’s mechanical engineering program in lieu of flowers.