A federal jury ruled Apple Inc. infringed on a University of Wisconsin patent when developing processors for some recent iPhones and iPads, the latest in a string of disputes over the technology undergirding smartphones.

The jury in U.S. District Court in Madison, Wis., found that the university’s 1998 patent on improving efficiency in computer processors is valid and that Apple AAPL, +1.57% illegally incorporated the patent’s technology in processors that help power some iPhones and iPads.