The lawsuit was filed early last year and accused Apple of using a processor technology developed by university researchers in Apple's A7 chip, which was used in its newest products at the time, including the iPhone 5S and iPad Air.
The jury began hearing the case last week, and on Tuesday it found Apple liable for infringement of all six patent claims, the verdict form shows.
Apple faces a maximum damages payment of $862.4 million, according to the news website Law360, which got the figure from a court order filed last month. It wasn't immediately clear when the award would be decided, and the sum could turn out to be less.
Apple didn't respond to a request for comment, and a spokeswoman for the Wisconsin Alumni Research Foundation, which manages the University of Wisconsin's patents and which brought the lawsuit, declined to comment.
The U.S. patent in question, number 5,781,752, describes a "Table based data speculation circuit for parallel processing computer." It was awarded to four researchers at the University of Wisconsin in July 1998.
WARF had already filed a lawsuit against Intel over the same patent. The chip maker settled that case before it came to trial by paying WARF a lump sum of $110 million to license the patent, according to a judge's order filed in the Apple case.
In its complaint, the university said Apple had filed patent applications that cite the '752 patent as prior art, suggesting Apple had been aware of it. It also said that Apple had a stated policy not to accept licensing proposals "from outside entities like WARF, making the litigation of this lawsuit necessary."