Robert H. Dennard, an engineer who invented the silicon memory technology that plays an indispensable role in all smartphones, laptops and tablets, died April 23 in Sleepy Hollow, New York. He was 91 years old.
The cause of death, at a hospital, was a bacterial infection, said his daughter, Holly Dennard.
Dennard's pioneering work began at IBM in the 1960s, when equipment to contain and store computer data was expensive, hulking (often room-sized machines), and slow. He was studying the emerging field of microelectronics, which used silicon-based transistors to store digital bits of information.
In 1966, Dennard invented a way to store a digital bit on a transistor: a technology called dynamic random access memory, or DRAM, which retains information as an electrical charge that slowly fades over time and must be periodically refreshed.
Their discovery opened the door to a previously unimaginable improvement in data capacity, with lower costs and higher speeds, all using small silicon chips.
DRAM has been the basis of constant progress in the decades since. High-speed, high-capacity memory chips contain and quickly transfer data to a computer's microprocessor, which converts it into text, sound, and images. Streaming videos on YouTube, playing music on Spotify or Apple Music, and using ai chatbots like ChatGPT depend on them.
“DRAM has made much of modern computing possible,” said John Hennessy, president of Alphabet, Google's parent company.
Dennard also devised a concept that has served as a roadmap for future advances in microelectronics. Debuted in an initial paper in 1972, and developed in another two years later, he described the physics that would allow transistors to shrink and become more powerful and less expensive, even as the power consumed by each would remain nearly constant.
The principle, known as Dennard scaling, complemented a prediction made in 1965 by Gordon Moore, who later co-founded Intel. Moore said the number of transistors that could be included on a silicon chip could double about every two years, and that computing power and speeds would accelerate along that trajectory. His prediction became known as Moore's Law.
Moore's Law referred to the density of transistors on a chip, while Dennard's scale mainly referred to power consumption, and in 2005 it reached its limits: transistors had become so small that they began to leak electrons, which caused the chips to heat up and consume more power.
But Mr. Dennard's approach to identifying challenges in the technology, researchers say, has had a lasting impact on chip development.
“Everyone who works in semiconductors studied their principles to get to where we are today,” said Lisa Su, CEO of Advanced Micro Devices, a large chipmaker and a former colleague of Dennard's at IBM.
Robert Dennard was born on September 5, 1932 in Terrell, Texas, the youngest of four children. His father, Buford Dennard, was a dairy farmer and his mother, Loma Dennard, was a homemaker who also worked in a school cafeteria.
The family moved east when Robert was a small child and he began his education in a one-room schoolhouse near Carthage, Texas. The family later moved to Irving, then a small town, when his father got a job at a fertilizer company there.
Growing up, Robert developed an appreciation for the arts, reading the stories of H.G. Wells and the poems of Ogden Nash that his older sister, Evangeline, had left behind when she left Texas to work as an Army nurse during World War II. In an oral history interview for the Computer History Museum In 2009, he recalled listening to an album of Sigmund Romberg operettas countless times. “She left me some really good things to start some kind of intellectual career,” she said of her sister.
In high school, he was a good student, especially in math and English, and had planned to go to a nearby university. But his aptitude for music offered him a different path. He played E-flat bass in his high school band, and when the band director at Southern Methodist University visited, he offered Robert a scholarship.
“That was my chance,” Dennard recalled.
Although music was his entry point, he earned bachelor's and master's degrees in electrical engineering in college. He later received a Ph.D. from the Carnegie Institute of technology, now Carnegie Mellon University.
In 1958, Dennard was hired by IBM, where he spent his entire career until retiring in 2014.
He was married three times. He and his second wife, Mary Dolores (Macewitz) Dennard, divorced in 1984, and in 1995 he married Frances Jane Bridges.
In addition to his daughter and his wife, Mr. Dennard is survived by another daughter, Amy Dennard, and four grandchildren. His son, Robert H. Dennard Jr., died in 1998.
Over the course of his career, Dennard produced 75 patents and received several scientific awards, including the National Medal of technology from President Ronald Reagan in 1988 and the Kyoto Prize in Advanced technology from the Inamori Foundation in Japan in 2019.
In the 2009 interview, when Mr. Dennard was asked what advice he would give to a young person interested in science and technology, he pointed to his own “very humble upbringing” and said that “anyone can get involved in this.”
“There are opportunities there,” he said. “These things don't happen by themselves. “It takes real people to make these advances.”
