It’s a hot summer day. You’ve been working hard and you’re burning up. You decide to take a break, so you wipe your brow and head inside to quench your thirst. What do you reach for? Whether your beverage of choice is lemonade or a, um, wheat-and-hop smoothie, you want it cold and you want it right now.
It’s that same thinking that has informed the way supercomputer makers have used water to keep the chips inside their number-crunching behemoths from succumbing to their own brand of heat stroke. Many liquid-cooled machines come equipped with electric chillers that keep the fluid that flows through them at a relatively brisk 15 degrees Celsius.
But a team of researchers at IBM Research in Zurich, Switzerland, reported in the 16 April issue of Science their discovery that warm water is just as effective as cold water at ensuring that chips stay within their rated temperature range. They proved it with a supercomputer they built called Aquasar. The 10-teraflop machine has 60-degree water flowing through its network of copper pipes. The researchers say these viaducts draw away enough heat to keep the microprocessors’ temperature from exceeding 75 degrees Celsius—well below their rated limit of 85 degrees, where they begin to malfunction.
Though chilled chips run faster and have a longer lifespan, there is a good reason to let the warm water flow. The IBM team says that getting rid of the chillers lets Aquasar operate using half the energy that would be consumed by a similar model that is treated to a cold drink. IBM says it hopes to narrow the performance gap by making warm-water heat removal even more efficient. Within five years, the company says, the tubes that now carry the water around the chips will run right through them.
Willie Jones is an associate editor at IEEE Spectrum. In addition to editing and planning daily coverage, he manages several of Spectrum's newsletters and contributes regularly to the monthly Big Picture section that appears in the print edition.