The suit, filed in Federal District Court in Delaware, alleges patent infringement on four patents originally filed in 1990, the year Rambus Inc. was founded. The patents, which can be accessed from the U.S. Patent Office's web site, include U.S. Patent Nos. 5,915,105; 5,953,263; 5,954,804 and 5,995,443.

The patents involve 141 different technologies that are fundamental to synchronous DRAMs and microprocessors, including delay lock loops (DLLs), double bus rate technology, and two-bit prefetch architecture technology. The technologies apply to synchronous DRAMs, modules, and microprocessors which interface with synchronous DRAMs, Rambus said.

The four patents were orginally filed in April 1990 by Rambus founders Mark Horowitz, Mike Farmwald and others. Avo Kanadjian, vice president of marketing at Rambus (Mountain View, Calif.), said Rambus is suing Hitachi because it failed to attend a follow-up meeting Rambus had requested to discuss claims presented at an earlier meeting last year.

"The only reason we are suing Hitachi is that they failed to respond to our requests for follow-up meetings during which Rambus had presented its patent analysis. We would prefer to negotiate and settle amicably, and we would hope and trust that all companies involved will do so," he said.

A spokeswoman for Hitachi said the company was trying to determine the facts, and was not prepared to comment. But she said it would be surprising if Hitachi had stonewalled Rambus' requests, saying that Hitachi employees "meet with Rambus people all the time."

Other companies making SDRAMs, MPUs, and other products apparently are continuing to negotiate with Rambus, though Kanadjian declined to comment on the status of those negotiations. Intel, for example, apparently would need the patents for use in its MPUs, but Kanadjian declined to comment on any Rambus-Intel negotiations.

"We are in negotiations with companies that use this technology, but it would be inappropriate to comment further on those negotiations, since they are confidential. Indeed, our patents cover fundamental aspects of synchronous memories. Other companies (besides Hitachi) will want to license this IP as well for non-Rambus products," Kanadjian said.

"An IP company"
Asked if legal actions and patent claims would discourage the DRAM vendors from putting their shoulders behind the nascent RDRAM technology, Kanadjian said the two issues should be considered separately.

"This does not relate to Rambus components. We are an IP company, which develops and licenses IP, and we are protecting our IP, just as TI and Qualcomm have protected and licensed their IP," he said.

Texas Instruments pursued all of the major semiconductor vendors for royalties relating to the Kilby patent, a fundamental patent relating to Jack Kilby's invention of the integrated circuit in 1958.

Qualcomm also has enriched itself through aggressively protecting its IP. In its most recent annual report, IP licensing accounted for nearly as much as the company's chip set sales.