An expert technical panel set up by the Italian court last week had upheld the validity of the Rambus patents, which the Los Altos, Calif., company claimed Micron had infringed. However, the judge Thursday overruled that finding and determined that Micron had not violated the patents.

Details of the decision were sketchy, but sources close to Micron said the judge determined that Rambus' synchronous patents use a multiplexed memory bus, something Micron's SDRAM do not use. The basis for the decision was similar to that used this month in a U.S. District Court in Richmond, Va., where federal judge Robert Payne dismissed patent infringement charges brought by Rambus against Infineon Technologies AG. In that trial, the judge also found that because Infineon's SDRAM do not use the same multiplexed bus described in the Rambus patents that no violation had occurred.

Rambus executives were not immediately available to comment on the Micron decision. Earlier this month a jury in the Richmond trial found that Rambus committed fraud by hiding its SDRAM patent applications while participating in an industry JEDEC panel drafting an open SDRAM standard. Based on the decision, Infineon has asked Judge Payne to declare the Rambus patents unenforceable. Payne is now expected to rule on the motion in July.

In a separate action, Micron, Boise, Idaho, has filed suit against Rambus in a Wilmington, Del., federal court seeking to invalidate the synchronous patents. U.S. District Court Judge Roderick McKelvie has set the case aside until Judge Payne rules on the outstanding unenforceability question. The Wilmington trial is now set to open Oct. 29.

In the meantime, a court in Mannheim, Germany, is due to rule in the next several weeks on Rambus' patent infringement suits against Infineon, and somewhat later on separate complaints filed by Rambus against Micron and Hynix Semiconductor Inc. (formerly Hyundai Electronics Industries Co. Ltd.).