For decades, computer engineers have treated waste heat as an unavoidable cost of computation. Hannah Early, however, believes it is a design problem. Early, 31, is the co-founder and chief technology officer of Vaire Computing, a startup developing energy-efficient computer chips that reuse power typically lost as heat. The approach, known as reversible computing, could eventually improve the energy efficiency of data centers, laptops, and mobile phones.
When conventional computer chips perform calculations, they erase information that is no longer needed. That process dissipates energy as heat. Early compares it to driving around town and braking at every intersection: the car loses momentum and requires additional fuel to accelerate again. Reversible computing aims to preserve that momentum. Instead of deleting information from intermediate steps, reversible circuits retain it and run calculations backward to recover some of the energy.
The concept of reversible computing was first proposed more than 50 years ago, but existing transistors and circuit designs made it impractical. Early has rethought the hardware required to recover energy efficiently. She designed a patent-pending resonator, a tiny chip component that stores recovered energy for reuse. “This is truly a glorious pendulum,” she says. Last year, Vaire Computing announced a major advance: a chip with a resonator that recovered more energy than it lost, even after accounting for the power required to operate its components. For a field that had remained largely theoretical, the results offered important proof that reversible computing could work in practice.
“It’s clear they have something interesting,” says Igor Markov, an electronic design automation researcher and former professor at the University of Michigan, Ann Arbor. However, he notes that the technology remains in its early stages. Vaire will need to produce “a series of increasingly realistic and convincing demonstrations” to gain the industry support required for commercialization.
She gradually became convinced that the connection between information, energy, and heat could transform computing forever.
Early’s path into chip design began earlier than most. She started programming at about age 9, initially writing high-level code for the web before learning other programming languages, including Perl and Java. Over time, she moved through increasingly deeper layers of computing, eventually reaching the transistor.
She later joined computational biologist Goss Micklem’s PhD program at the University of Cambridge. Her research initially focused on how materials such as DNA could be used to perform computations. A few months later, Micklem sent her the 1999 doctoral dissertation of Michael Frank, a pioneer in reversible computing. Early read it once, remained skeptical, read it again, and then set it aside for several weeks. Gradually, she became convinced that the relationship between information, energy, and heat could change the future of computing.
That realization redirected her doctoral research. Early began studying the physical limits of computation and developed software capable of converting conventional programs into reversible ones. “Ultimately, I didn’t allow my name to appear on any of her papers because I didn’t feel I could stand up and talk about them properly,” Micklem recalls. “It was hers.”
After completing her degree in 2021, Early met technology entrepreneur and investor Rodolfo Rossini. The pair co-founded Vaire Computing that same year. Since then, the company has raised more than $12 million, hired Frank as a senior scientist, and begun translating its vision of reversible computing into working hardware.
Developing the technology, however, required years of experimentation. During the winter of 2022 in Grinnell, Iowa, when outdoor temperatures reached approximately -40 degrees Fahrenheit, Early spent weeks in the basement of her now-wife’s apartment repeatedly sketching the core circuitry needed for reversible logic on a whiteboard. When the design finally came together after the couple traveled to Las Vegas to escape the cold, the moment felt less like a sudden breakthrough and more like a gradual sense of relief. “I’m not completely out of my depth,” she remembers thinking.
Early and her colleagues now face the challenge of adapting their fundamentally different chip architecture to existing devices and manufacturing systems. She believes the opportunity is significant. Rather than simply improving conventional processors, Vaire Computing aims to rebuild computer hardware from the ground up around the principles of reversibility. “I want to address every part of how computers are built and rethink them from these perspectives,” Early says.
Source: www.technologyreview.com