By James R. Hagerty

When Diosdado Banatao met Maria Cariaga at a party in 1968, they were both Filipinos who had recently arrived in Seattle.

The son of a rice farmer, Banatao was working as a junior design engineer for Boeing. Cariaga, whose father was a lawyer, was doing clerical work for an insurance company while preparing to study educational psychology.

When he asked her for a date, she expected dinner at a nice restaurant. Instead, he bought Twinkies and orange juice from a vending machine. They dined in his car. Even so, she came away with a positive impression of a thrifty, humble and ambitious man, who was sending money home to his family. They married in 1972.

Over the next 50 years, Banatao had pioneering roles as an engineer and entrepreneur in Silicon Valley, helping to design the electrical circuitry needed to make personal computers and cellphones into affordable tools and playthings with dazzling graphical displays.

Banatao, who died Dec. 25 of complications from dementia at the age of 79, began his chip-design career in the early 1970s, working for National Semiconductor. He moved on to Commodore International, where he designed circuitry for calculators, and later to Seeq Technology, working on chips for computer networks. Those jobs gave him an inkling that computers would someday fit in our hands and pockets.

Join the club

In the 1970s, Banatao joined gatherings of the Homebrew Computer Club, a band of hobbyists and tinkerers that included Steve Jobs, Steve Wozniak and others who envisioned machines that could perch on desktops.

In the early 1980s, Banatao spent about $2,000 to buy a Hewlett-Packard computer, a splurge for him at the time. "I wanted to see how it works," he said in a 2013 oral history recorded by the Computer History Museum. "It was more of a box that is used for an engineering lab, not a tool for general purpose. I said, 'Why did I buy this?' But, you know, you have to learn."

During a family trip to Lake Tahoe, he toted two bags of notes. "I started to write down the basic requirements of a personal computer," he said. Banatao gave himself an edge by mastering both software and chip design, while many others in Silicon Valley had expertise in one or the other.

Itching to leap from employee to entrepreneur, he warned his wife that a flop might mean no more private schooling for their children. She was willing to take the risk.

Starting in the mid-1980s, he co-founded three chip-design firms. The first, in 1984, was Mostron, focused on designing low-cost chipsets -- clusters of chips that manage the flow of data between the central-processing unit and other parts of a computer. Because IBM was moving into the market for personal computers, Banatao decided to design chipsets that would work with IBM-compatible machines.

His notes "took over our dining room at home," much to his wife's chagrin, Banatao said in the oral history. "I read the entire software code of IBM," he said. "There were secrets in there." If the circuitry didn't mesh perfectly with the code, computers would crash.

At Mostron, "we ran out of money," Banatao said. So, in 1985, he helped start up Chips & Technologies, where he found success in the chipset market. That firm was sold to Intel in 1997, long after Banatao had moved on, for about $420 million.

In the late 1980s, Banatao co-founded S3 to design chips that improved computers' graphic displays. The name S3 was chosen, he said, because it was his third startup.

He was an early convert to the practice of relying on outsiders for fabrication and other services. "People say we don't have companies, we have virtual companies," Banatao told the New York Times in 1994. "Where once it was a one-stop shop, we have partners who do wafers and who do packaging and who do tests."

In the mid-1990s, Banatao jumped from chip design into venture capital. He worked with Mayfield Fund and later founded his own firm, Tallwood Venture Capital. His focus, he said, was on "difficult-to-do technology."

One of his early investments was in SiRF Technology, which developed navigation chips that put GPS functions into cellphones and other devices. Other investments included Marvell Technology, NewPort Communications and Cyras Systems. He also invested in Inphi, a maker of components for high-speed digital networks, where he served as chairman.

Bamboo math

Diosdado Pamittan Banatao (pronounced Ba NAH tao), known as "Dado," was born May 23, 1946, in the farming town of Iguig in the Cagayan Valley region of the Philippines. (His first name means "God-given.") While his father, Salvador, farmed, his mother, Rosita, worked as a housekeeper.

Young Dado grew up in a house with no electricity and walked barefoot to school, where he used bamboo sticks to learn arithmetic. Most of his schoolmates dropped out after six years to work on family farms. But Banatao's father wanted him to continue with his studies and sent him to a Jesuit high school, where he was a boarding student.

"My job was to study," Banatao said in a 2016 documentary. "When my friends played basketball, I studied." He went on to earn an electrical engineering degree at the Mapúa Institute of Technology in Manila, now Mapúa University.

Finding no engineering jobs he considered suitable in the Philippines, he began training as a pilot for Philippine Airlines. Then he learned that Boeing was recruiting engineers from Mapúa. Though not sure he wanted to give up his job as a pilot, Banatao filled out an application and ended up accepting a job in Seattle in 1968. He earned a master's degree in electrical engineering at Stanford University four years later.

His wife survives him, along with two brothers and a sister, three children and nine grandchildren.

Banatao provided funding and chaired the advisory board at the Center for Information Technology Research in the Interest of Society, which supports research at University of California campuses. He also advised the Philippine government on technology and funded scholarships and training programs for Filipinos in science, technology, engineering and math. His scholarships came with personal mentoring, not just a check.

"I came from almost nothing," he told the Manila Bulletin in 2011. "I was fortunate that my parents worked really hard to get us educated in some of the best schools."

Write to James R. Hagerty at reports@wsj.com

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January 15, 2026 10:00 ET (15:00 GMT)

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