Electronics giants Sony and Toshiba have been sued in a patent dispute that involves the main chip Sony's PlayStation 2 video game console uses.

A representative for the Wisconsin Alumni Research Foundation (WARF), the group that administers patents researchers at the University of Wisconsin obtain, said it filed the suit last week in U.S. District Court in Madison.

Although it did not immediately give details about the specific patent involved, the group said the dispute is based on the "Emotion Engine," the custom chip that's designed and manufactured in a joint effort between Sony and Toshiba.

The patent covers advanced chipmaking technologies and has been licensed by a number of technology companies, according to the WARF representative, who said Sony and Toshiba have so far declined to obtain a license. "We hope the lawsuit will encourage them to bargain in good faith," the representative said.

Sony has sold more than 60 million units of the PlayStation 2 worldwide, giving the company a broad lead in the video game hardware market.

Unlike competitor Microsoft, which used off-the-shelf Intel chips for its Xbox game machine, Sony has designed and built its own chips. The electronics giant is in the midst of a joint effort with Toshiba and IBM to create the "Cell" processor, seen as the most likely candidate to power the next version of the PlayStation.