WARF is the arm of the University of Wisconsin-Madison science and research team that deals with getting and enforcing patents.
According to reports, it is enforcing a patent that covers the making of a chip, rather than the chip itself. WARF says this patent is being infringed by the making of the PS2's so-called Emotion Engine integrated processor.
A WARF spokesman told CNet News that other companies had licensed its patent technology. He said of Sony and Toshiba's refusal, "We hope the lawsuit will encourage them to bargain in good faith".