William Lee of WilmerHale. May 2, 2013.

Apple Inc. has escaped a $506 million patent infringement judgment over semiconductor technology.

The U.S. Court of Appeals for the Federal Circuit on Friday threw out the judgment won by the University of Wisconsin's technology transfer arm in a 2015 jury trial. “No reasonable juror could have found infringement based on the evidence presented during the liability phase of the trial,” Chief Judge Sharon Prost wrote for a unanimous panel.

The case has been fought tooth-and-nail at trial and on appeal by Wilmer Cutler Pickering Hale and Dorr for Apple and Irell & Manella for the university. Wilmer partner William Lee and Irell partner Morgan Chu squared off for a marathon one-hour-and-40-minute hearing in July before the Federal Circuit.

Wisconsin Alumni Research Foundation v. Apple involves data speculation circuits that help predict when to process instructions out of order and therefore more efficiently. University researchers helped pioneer the technology in the 1990s. The Wisconsin Alumni Research Foundation accused Apple's A7, A8 and A8X processors of infringing.

Irell and WARF settled similar claims against Intel for $110 million. Apple chose trial and got hit with a $234 million verdict in the Western District of Wisconsin. With royalties, supplemental damages, interest and costs the total came to $506 million. A second trial targeting a later generation of Apple's processors has been on hold pending the appeal.

U.S. Patent 5,781,752 describes a prediction table that communicates with a data speculation circuit to create an entry listing a “particular” load instruction associated with a mis-speculation. U.S. District Judge William Conley ruled at trial, and the Federal Circuit affirmed Friday, that “particular” means a single load instruction.

Apple argued that only 4,096 load tags are possible on its processor, so it uses a hashing algorithm to generate multiple load instructions for the same tag. “Each load tag can therefore be associated with a group of load instructions—namely, all of the load instructions that hash to the same load tag,” Prost wrote.

“Given that only 4,096 load tags are possible, and that Apple's operating system alone contains millions of load instructions, the only reasonable inference to draw is that load tags will always represent multiple load instructions,” Prost wrote. Therefore, the “particular” limitation of the '752 claim was not satisfied.

There was one silver lining for WARF. The Federal Circuit rejected Apple's challenge to the validity of the '752 patent.

Judges Kathleen O'Malley and William Bryson concurred in Prost's opinion.