Judge Ronald Whyte of the U.S. District Court for Northern California stayed the coordinated patent infringement cases brought by Rambus because of a conflicting ruling last month from a district court in Delaware about whether or not the patents are enforceable, according to court documents posted online.

The stay extends to other litigation by Rambus against DRAM makers Micron Technology, Samsung Electronics, Hynix Semiconductor and Nanya Technology. Millions of dollars in licensing fees are at stake in the ruling, and cover patents that go into common DRAM technology found in nearly all computers produced today.

Whyte wrote that the stay would remain in place until an appeal to the Delaware court's decision had been ruled upon or by a further order from his court.

Rambus' stock tanked in reaction to the court decision in after-market trading, falling 22.4 percent to US$6.95 by the end of the session.

"While we are disappointed with the stay of the coordinated cases, it is our expectation that the conflicting opinions of the district courts regarding document spoliation will go up together on appeal," said Tom Lavelle, senior vice president and general counsel at Rambus, in a statement.