Rambus has accused Micron of patent infringement, alleging the US memory maker has sold products containing its DDR 2, GDDR 2, GDDR 3 and other "advanced" memory technologies without permission.

Rambus is already battling Micron in the Delaware District Court, but the new filing, made late last week, opens a new front in the war, this time in the US District of Northern California - Rambus' preferred location for litigation.

Micron sued Rambus in Delaware in 2000, alleging the memory technology company engaged in anti-competitive behaviour. Micron asked the court to invalidate a number of Rambus' DDR-related patents. Rambus responded in 2001 with a counterclaim that's the essence of the allegations made in its latest, Californian filing.

That action comes as a result of limitations on Rambus' legal freedom of movement being lifted by the Delaware Court. ®