Ben Rosen helped turn a rejected pitch for an IBM PC add-on into a wager on a fully compatible portable computer that helped launch Compaq. Rosen, the engineer, technology analyst, venture capitalist and founding Compaq chairman, died on August 23, 2026, at 93.

The wager took shape soon after IBM introduced its personal computer. In an oral history preserved by the Computer History Museum, Rosen recalled that three former Texas Instruments engineers first brought his venture firm a proposal for an aftermarket disk drive. Rosen and his partner, L. J. Sevin, declined that idea but encouraged the group. The engineers then developed a portable machine designed to run the same software and peripherals as IBM's PC. "We made a bet that the world would be IBM-compatible," Rosen said. The choice helped make compatibility a central promise of the personal-computer market.

Rosen reached that decision by a route through engineering, business and finance. Born in New Orleans on March 11, 1933, he followed his older brother Harold to Caltech and earned a bachelor's degree there in 1954. A master's degree from Stanford followed in 1955. He worked as an electronics engineer at Raytheon and Sperry Gyroscope, earned an MBA from Columbia in 1961, and became an analyst at Coleman and Company and later a vice president at Morgan Stanley, according to Caltech.

He also made places for a young industry to meet. Rosen recalled convening the first Personal Computer Forum in 1979, when about 50 people and six companies attended, including Apple and RadioShack. In 1981 he and Sevin founded Sevin Rosen Funds, combining technical judgment with early financing.

The firm backed more than 100 technology start-ups, among them Citrix Systems, Electronic Arts, Lotus Development and Silicon Graphics. Rosen served as Compaq's chairman for 18 years and promoted an open PC architecture in which products from different makers could work together. By 1999, the Los Angeles Times described Compaq as the world's largest personal-computer maker, a measure of how far the portable-computer wager had traveled.

Computerworld included Rosen among 25 people who changed the computer industry in 1992. IEEE awarded him its Founders Medal in 1999. Caltech gave him its Distinguished Alumni Award in 2007 and its highest honor, the Robert A. Millikan Medal, in 2018.

Caltech was the institution to which Rosen returned across decades. He joined its Board of Trustees in 1986, chaired the board from 2001 through 2005 and became a life member of the Caltech community. In 2008, the Benjamin M. Rosen Family Foundation gave $18 million to establish the Donna and Benjamin M. Rosen Bioengineering Center. The institute's announcement described a center designed to bring engineering methods to biological questions and sustain ambitious early research. Rosen and his wife Donna later founded KentPresents, an annual nonprofit ideas festival in Connecticut.

His public service also reached the New York Philharmonic, the Metropolitan Opera, Memorial Sloan Kettering Cancer Center and Columbia Business School. He was survived by Donna, his sons Jeffrey and Eric Rosen, and his stepdaughter Melanie Perret.

Rosen's work remains visible in the compatible computers that became an industry norm, the companies that carried early financing into global markets, and the Caltech center connecting engineering with biology. From a portable-computer proposal to long-term support for scientific research, he repeatedly put structure and capital behind ideas that others could build upon.