A top U.S. business regulator ruled on Wednesday that computer technology developer Rambus Inc. (RMBS) unlawfully monopolized markets for four memory chip technologies, sending its shares down as much as 30 percent.

The ruling from the U.S. Federal Trade Commission puts at risk tens of millions of dollars in royalties that Rambus, which has no manufacturing facilities of its own, earns from licensing its technology to other chipmakers.

"It's definitely a big setback for the company," said Daniel Amir, an analyst with WR Hambrecht. "It's all downside in a way. When you're losing a case against the government, you're dealing with broad implications."

In a statement on its Web site, the FTC said that Rambus, "through a course of deceptive conduct," was able to distort industry standards for a type of memory chip known as dynamic random access memory, or DRAM.

That allowed the company to "engage in an anti-competitive 'hold-up' of the computer memory industry," the FTC said.

The remedy sought by the FTC would bar Rambus from enforcing existing licensing agreements, along with some patents. The FTC said it ordered more briefings to determine the appropriate remedy.

Rambus shares were down $3.93, or 23.1 percent to $13.05 in active afternoon trade on Nasdaq; earlier they fell as low as $11.80.

The stock, which closed as high as $44.50 in April on expectations of big legal payouts, has lost almost all its gains and now trades 1.3 percent above its year-ago level.

Los Altos, California-based Rambus believes it can continue with its licensing activity and existing lawsuits, including patent cases against Micron Technology Inc. (MU) and South Korea's Hynix Semiconductor Inc.

"We believe it highly likely (that) we will be taking an appeal from the liability that has been found," John Danforth, senior legal adviser at Rambus, told a conference call.

The FTC brought antitrust charges against Rambus in June 2002, and a trial took place in 2003.

In 2004, a U.S. administrative law judge handed Rambus a victory by dismissing charges that it illegally monopolized key chip technologies. Later that year, the FTC staff asked the agency's five commissioners to overrule the decision.

For years, Rambus has been seeking royalties from some of the world's largest memory-chip makers on patented technology it asserts is used in DRAM chips used in almost all computers.

Last month, Rambus said it would accept a damage award of $134 million in the Hynix case, in which a U.S. jury found the South Korean chipmaker knowingly violated Rambus patents.

"This definitely puts some stains, I would say, on Rambus's case," Amir said. "It probably pushes out any potential settlements. If I'm Hynix, I would say I probably have some basis for an appeal now."

In 1990, Rambus filed for a patent for a new type of memory called RDRAM. The company then became a member of an industry group called JEDEC that was trying to agree on standards for another memory technology, called SDRAM.

The FTC cited a half-dozen instances in the mid-1990s in which it said Rambus had secretly applied to amend a patent to cover technologies that JEDEC was considering for SDRAM.

It said Rambus executives had misled JEDEC officials when asked if the company had patented key technologies. Rambus has maintained it never did anything to violate JEDEC's rules.