Computer chip manufacturer Rambus Inc. has sued IBM Corp. in an effort to overturn a U.S. Patent and Trademark Office decision that an IBM patent for memory controller technology predates a Rambus patent for the same invention. Rambus filed suit Monday in the U.S. District Court for the Northern District of California, claiming the USPTO Board of Patent Appeals and Interferences “committed errors of fact and law” in its June 24 ruling for Big Blue. The suit asks the court to reverse all of the board's rulings adverse to Rambus, and declare that IBM is not entitled to the earlier priority date and that the claims in the defendant's patent application are unpatentable. Rambus is represented by Finnegan.