Rambus, which is involved in extensive patent infringement litigation, had accused a long list of companies of infringing six patents for, among other things, memory controllers, which retrieve information when it is needed, and high-speed chip-to-chip communication systems.

In the past year, Rambus settled patent litigation with Nvidia Corp, Broadcom Corp and Freescale Semiconductor Holdings I Ltd. In addition, one of the six patents was dropped from the complaint.

The decision by ITC Judge Theodore Essex is not final. The full commission is expected to make a ruling in July.

"We have yet to receive the decision, but are disappointed with the initial determination of no violation," said Thomas Lavelle, senior vice president and general counsel at Rambus in an emailed statement. "We believe in the strength of our portfolio and remain committed to protecting our patented inventions from unlicensed use."

Rambus' share price has been volatile due to its court fights. The company's shares rose sharply in early February following news it settled patent disputes with archrival Nvidia. And its share price dropped almost 60 percent late last year after the company lost a $4 billion antitrust lawsuit against Micron Technology Inc and Hynix Semiconductor Inc.

Three of the five patents at issue in this case - collectively known as the Barth patents - have been declared invalid by an appeals board at the U.S. Patent and Trademark Office. Two were declared invalid in September and a third in January.

But the patents remain valid during the appeals process, which has not yet been exhausted.

Rambus has aggressively used the three Barth patents to pursue infringement claims against technology companies.

The case at the International Trade Commission is Number 337-753.

(Reporting By Diane Bartz; editing by Bernard Orr and Andre Grenon)

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