For several years, David Bollig described the work of one of his computer firm’s better customers — a university research lab in California — to help suppliers and other customers understand what his company can do.

“I would say ‘There’s this cool one where they’re trying to discover gravity waves and prove Einstein’s theory,’ ” he said. “And people would just kind of roll their eyes.”

Then, in February, those researchers revealed that they had detected a gravitational wave from the collision of two black holes, a breakthrough that is likely to lead to a Nobel Prize.

The clusters of high-powered computers built at the firm Bollig and his wife, Cynthia, own in Burnsville, called Northern Technologies Inc. or Nor-Tech for short, sorted through billions of signals gathered by giant detectors in Louisiana and Washington state.

“Now people are saying ‘That’s the thing you were telling us about,’ ” Bollig says. “People call and ask us to explain the signal analysis we can do.”

The couple started the company as an assembler of custom-ordered PCs in the 1990s, a time when it seemed that nearly every strip mall and industrial park in America had a mom-and-pop computer operation. Nor-Tech still puts together or customizes PCs, mainly for school systems and midsize businesses around the Twin Cities.

But when margins collapsed on PCs in the late 1990s and early 2000s, the Bolligs decided to invest at the high-end of the PC business. They hired engineers who knew how to put together the highest-performing microprocessors into clusters that could share the load of running a program or sorting data.

A financial backer in Texas initially resisted their plan. “Everyone pulled back when PCs started slowing down,” Bollig said. “Very few people made hard-core investments in new areas and I’m glad we did.”

The investment positioned the company to be ready for when costs came down for clustered systems and more software would be written for them.

Today, hundreds of microprocessors can cluster onto systems that take on tasks that, years ago, were the province of supercomputers. For many small businesses or university researchers, a cluster computer that sells for just a few thousand dollars can take the place of a powerful PC and have the advantage of being easily upgraded.

“If you buy a high-end [PC] workstation, it’s not going to go any faster,” Bollig said. “With a cluster, we just add one more node to it, you might get a 30 percent jump in speed.”

While the computer industry’s powerhouses, Hewlett-Packard, Dell and Lenovo, focus on building the largest clustered systems, Nor-Tech has found a niche with smaller systems. The company, which employs 35 people, had $24 million in revenue last year.

“This area that has exploded is the cluster that runs between $50,000 and $250,000,” Bollig said. “Most people now are finding software that can run parallel [on multiple processors]. As that happens, scientists who used to wait a few days for a result can get it in a few hours or less.”

It takes about a month for Nor-Tech to get components, build, install software, test and deliver an order. The longest part of the process involves running a completed system at full power for several days. With large clusters, the process, called “burn in,” generates enough heat to warm the entire building. “I love to find a way to utilize the heat that comes off those things,” Bollig said.

Late one night a few weeks ago, Bollig saw a TV documentary about another customer, the IceCube Neutrino Observatory, for which Nor-Tech has provided computing clusters to its lab at the University of Wisconsin. He tried to wake up his wife to see it but she told him to record the show so she could watch it in the morning.

“They’ve taken a cubic kilometer and they’ve drilled these holes into the pure ice in Antarctica and they placed a large line with these basketball-sized sensors, thousands of these sensors deep in the ice,” he explained.

“And they’re looking for neutrinos that are coming from outer space.”