The lawsuit, which was filed yesterday in a federal court in San Jose, California, claims that the US Patent and Trademark Office made numerous mistakes in its decision that IBM did not violate a patent Rambus filed in 2002.
The patent relates to a memory controller which communicates to a memory subsystem via an independent point-to-point link.
“The board committed errors of fact and law in its orders, decisions, and judgment,” Rambus said, asking that the earlier ruling from June 24 be overturned as a result of this.
This is not the first time Rambus has sued a rival over patent infringement. Most recently it has been in a bitter battle with Nvidia, which Nvidia eventually lost at the end of July. Nvidia threatened to appeal the ITC ruling, but eventually signed a deal with Rambus earlier this month.
In June Samsung paid out $900 million to Rambus after the two made a licence agreement. At the time Samsung was one of the list of companies, including old Rambus enemies Hynix and Micron, that Rambus intended to sue for antitrust practices.
One of Rambus’ most pivotal lawsuits was against Infineon in 2000. Prior to this a number of smaller companies settled with Rambus, but the Infineon case provoked outrage among chip vendors including Micron and Hynix, both of which joined forces with Infineon to counter-sue Rambus. They accused it of fraudulently claiming it owned SDRAM and DDR technology. A 2001 ruling found Rambus guilty of fraud, but this was overturned in 2003.
Rambus again sued Infineon in 2004 and this latest case was eventually settled in 2005, with Infineon paying $47 million in licensing fees. An FTC investigation of Rambus over anti-trust practices in 2003 was dismissed in 2004, freeing Rambus up to sue dozens more companies over patent infringement.
Given the latest ruling in favour of Nvidia, and how lucky Rambus has been with appeals, it may only be a matter of time before IBM is forced to cough up a large sum of money to license the relevant patent.