U.S. District Judge William Conley in Madison added $272 million to a $234 million jury verdict the Wisconsin Alumni Research Foundation won against Apple in October 2015. Conley said WARF is owed additional damages plus interest because Apple continued to infringe the patent, which relates to computer processor technology, until it expired in December 2016.

Apple is appealing Conley's ruling, according to court papers. An Apple spokesman did not immediately return a request for comment.

WARF sued Apple in 2014, alleging processors found in some versions of the iPhone infringe on a patent describing a "predictor circuit," which improves processor performance by predicting what instructions a user will give the system. University of Wisconsin computer science professor Gurindar Sohi and three of his students obtained the patent in 1998.

Cupertino, California-based Apple denied any infringement during a 2015 jury trial and argued the patent is invalid. Apple also urged the U.S. Patent and Trademark Office to review the patent's validity but the agency rejected that bid.

WARF brought a separate lawsuit against Apple in 2015, alleging chips in later versions of the iPhone infringe the same patent. Conley said he would not rule in that case until Apple has had an opportunity to appeal the 2015 jury verdict.